To my knowledge it is not an intentional feature. It is something that has been happening for a long time and happens with Gauss often as well. I hear devs constantly try to fix it and even go as far as to change Magnum parameters like splash damage and projectile speed to "experiment" with the effects. I don't know if there's a solution right now other than refreshing your game or clearing the game cache.

If you mean your unaltered Magnum is moving left and right, it was changed a while back.
Currently, Magnum by default rotates left/right. To move it up/down, you need one of these 3 augments:
- Reinforced Gun Carriage
- Automatic Gunpowder Loading Mechanism
- Mortar
For more information on these augments, see this page: https://en.tankiwiki.com/Augments_for_Magnum?attempt=1

Energy gold boxes give you 1 energy for the Dark Matter Minigame.
M-M-M-MONSTER KILL doesn't really give anything. It just kills you and anyone around you when you touch the box.
Premium account golds give you a certain number of days of premium account.

First off, you might just be really unlucky with enemies getting crits a lot, or they were using Hornet/Dictator OD which guarantee crit damage.
 
But let's look at some augments that increase normal damage/critical chance/damage:
- Adrenaline (Universal): Increases damage by 20-29% depending on the turret and their health
 
- Incendiary Mix (Firebird): Increases normal and critical damage by 20%
 
- Corrosive Mix (Freeze): Increases normal and critical damage by 10%
 
- Blunderbuss (Hammer): Increases critical chance to 50% (No longer increases critical damage since the last patch update)
 
- Heavy Plasmagun (Twins): Increases normal and critical damage by 35%
 
- High Precision Aiming System (Smoky): Increases normal damage by 40% and critical damage by 10%
- Supercumulative Rounds (Smoky): Increases critical damage by 50%
- Sorted Ammunition (Smoky): Every 4th shot is critical
 
- Uranium (Striker): Increases normal damage by 50%
 
- Sledgehammer Rounds (Thunder): Increases normal damage by 45% at melee range
- Strict Ammunition Load (Thunder): Every 3rd shot is critical
- Hyperspeed Shells (Thunder): Weak damage percentage is 300% (deals 1350 at long range)
- Vacuum Shells (Thunder): Increases splash damage to 220%
 
- Uranium (Scorpion): Every 3rd shot is critical
 
- Large Caliber Rounds (Railgun): Increase normal and critical damage by 33%
- Round Destabilization (Railgun): Increases critical chance to 50%; Increases critical damage by 20%
- Hyperspace Rounds (Railgun): Increases penetration by 200% (Damage will increase after each pierced tank)
- Hyperspeed Shells (Railgun): Weak damage percentage is 300% (deals 2010 damage at long range)
 
- Short-Band Emitter (Shaft): Increases normal arcade damage by 35% and arcade critical damage by 33%
- Heavy Capacitors (Shaft): Increases maximum scope damage by 25%

Do you have a drone equipped? You need a drone to use supplies.

It depends. Since the shells are long range, you can ricochet at any distance. On a map with many vertical walls or surfaces, you can hit medium range targets that are hiding behind walls. On a map like Brest, it's possible to hit people hiding behind the wall at the top of the base. Like this:

Missiles don't have critical shots, only shells. By powercreeps, I mean Uranium Shells is a direct upgrade from Explosive Shells. It has the advantages of Explosive Shells plus more benefits, and none of the downsides of Explosive Shells.

Brutus
Containers
New Modifications System
From Alteration to Augment
Critical Damage
"Balance" Changes
Jack-in-the-Box
Meta Gear?
Status Effects
Overdrives, or Meta Gear? pt. 2
In conclusion? The game can be funbut it is very unfair and pay to win. Prepare to die often and feel powerless. Don't take it seriously and have as much fun as you can, and feel free to quit if you feel frustrated. I'm sure there are lots of things I missed, so please look to other people's responses for a more comprehensive understanding of modern TO. ^^

There are multiple possibilities. Critical damage ignores turret modules. Some augments and drones increase damage to make one-shots possible. And often you have both- augments that increase critical damage/chance combined with strong drones. Additionally, damage numbers are higher than ever now since a global update in June that significantly reduced TTK. One shots are pretty common nowadays, and moreso with light hulls.

You can no longer unequip drones
(Note) If you want to save batteries, equip the «Brutus» drone
To get access to the following supplies, you need to have a drone equipped: «Boosted Armor», «Boosted Damage», and «Speed boost».
What supplies are usable has nothing to do with the amount you have.

The servers are dying again.

Yes, it does.

I have a similar problem but I actually know why it's happening. I got an augment for Crusader but I don't actually own Crusader, so I'm unable to open augments for Crusader to make it go away. It thinks I just haven't checked it out when I don't own the hull at all. ?

Plasma Turbo Accelerators.

A long time ago, devs had the amazing idea of "merging" the buy and upgrade buttons to "simplify the upgrading process for new players". You can no longer MU if the next Mk level is available, regardless of MU level. You will have to pay the full price of the next Mk level. Best to wait for upcoming discounts. Honestly, it's best to avoid micro-upgrading nowadays since you rank up so fast. Just save up for each Mk level and only MU at Mk7.

In the latest update, you need a drone equipped in order to use supplies. Check to see if you have a drone equipped. If not, start with the Brutus drone. It costs 1000 crystals and doesn't consume batteries.

Defender and Lifeguard give you near-infinite Boosted Armor uptime.
Booster, Blaster, and Assault give you near-infinite Boosted Damage uptime.
Trickster gives you near-infinite Speed Boost uptime.
Hyperion gives you infinite supply uptime.
Crisis lets you switch to whichever supply you want whenever you want.
Assault gives you infinite supply uptime as long as you get kills consistently.
Miner significantly reduces mine cooldown.

Indeed, Helios is not available for purchase. You can only get it through Ultra Containers and special giveaways.
For example, in the Summer Major Tanki Fund, Helios was one of the prizes. Since the fund exceeded the level required to obtain Helios, everyone who bought at least one of the Fund offers got Helios.
The devs also mentioned in the latest V-LOG that they will give Helios to the top 10 players who earn the most stars in this challenge.

Oppai did answer your question, albeit somewhat indirectly. May I take a shot at explaining more thoroughly?
Before the update, there were 2 types of status Teslas:
- Endothermic (Freezing), AP, Jammer, and EMP Teslas were "Electroturret" augments because they worked off of the Electroturret template- increased ball speed, range, and warmup time. Status effects were inflicted through high-speed ball lightning, at the cost of ball lightning damage.
- Shocking (Stun) and Exothermic (Burning) Teslas followed the Minus Field template- ball lightning worked just like stock except it would ricochet up to 10 times and deal a respective status effect upon hitting an enemy.
The aforementioned update changed almost all status Tesla to follow the second template. Ball lightning has stock warmup time, stock speed, and stock damage. It will also bounce up to 10 times. The ability to bounce your ball lightning combined with a slower ball speed now allows for you to set up "status effect minefields" and control a certain area by releasing multiple lightning balls. Not only that, status effects can also be applied via a critical hit, which is a massive buff as you will be able to inflict effects consistently through Dictator or Hornet's Supercharge. On a somewhat related note, according to yesterday's Patch Notes, devs are intentionally giving status augments two ways to inflict effects: Through random critical hits, and through a guaranteed method (e.g., status Hammers can inflict effects through both critical hits and the last shot of a clip, and status Gausses can inflict effects through both critical and salvo hits).
Remember how I said almost every status Tesla follows the Minus-Field template? Jammer Tesla now works differently from other status Teslas, as it was changed to follow other turrets' Jammer augment precedent: Every shot will apply Jammer for 3 seconds. According to the DE Wiki, it still follows the Electroturret template, but its main forte is applying Jammer consistently on every chain hit.
As TheCongoSpider would say, check out the DE Wiki for the most precise and up-to-date information.