On mountainside, the staircase up to the roof has a slope on the stairs to keep the camera steady while going up the stairs, instead of the view jittering up and down and what not. Because of this slope, c4 and sensors can get into little cracks of the staircase and be undisarmable by the player, which makes certain rigs quite literally impossible to disable.

Heres a screenshot of a c4 in that spot

I placed down a C4 in a hallway, and was camsticking it, waiting for an enemy. At some point I accidentally pressed right click but I never let go, therefore the c4 never blew up. Someone threw a nade and I got ragdolled, and when I got back up, the C4 instantly blew up without any sound or green light and without any further button inputs

Heres a GIF of the bug happening

As of the first Steam update, death colliders, at least on custom maps, are entirely nonfunctional. (This means that on TrainHeist players can safely jump off of the train and on HelixArena they can step off of the map and fall forever, never dying.)

My game became unresponsive while I was playing a game on Mountainside. I wasn't doing anything in particular (just walking around in the basement), however the helicopter was currently doing a bombing run. Attached is the log, hopefully its useful.

The bathroom stall doors don't have a scroll wheel tool tip. The door frame (near Lab C) leading into garage has a scroll wheel tool tip, even though there isn't a door.

You can jump upwards while playing the "falling hands" animation by holding space a little before.

With the help of teammates or explosives, you can force yourself into the vending/soda machines in the B2 breakroom (upstairs). From there, you can see outside the machine as if it were one-way glass, and shoot out. Furthermore, you can get pushed/explode yourself even further backwards into the wall separating the breakroom and the back rocks/water. This wall is thick enough to walk in, and you can roam around in the walls of building 2. From inside, you have a view of a large portion of B2, and can shoot and grenade these visible areas while remaining untouchable. 

Detailed procedure:

if someone swings a door at you while you have a grenade out it guntucks you, but it also continues the animation making you think your grenade is fine. Works on walls too not exclusive to doors

I've run into an issue where I will open fire on an enemy but it will register as friendly fire and I'll even receive the warning for it.

your radio will stay activated after being ragdolled from: falling, being pushed, or slipping

When you jump in a certain spot on riverside (gallery window frames), you can see through the map while props disappear, including inside vent shafts. Bug found by montresor and Asper29. Thank you rob!

https://gfycat.com/FaroffSereneDogfish

Stand in the corner of the first window frame from the rocks and jump.

If you use a camstick to look at a lms zone they do not render.

if you press the heli button on MS to fast the helicopter will not be called in

it is on the rocks above the deathzone

So i stopped playing the game a long time ago due to a bug (I assume) where my game wouldn't launch. I have returned to play the game recently and the same issue occurs.However the game has launched on versions between the last time i had the problem and now so i have been able to play.  Loading occurs on my mouse but no error message or anything. I have not got windows defender on.

I have redownloaded the game several times to attempt to fix this but nothing seems to work. 

Any help is appreciated.

On Riverside in Lab A placing a sensoron the underside flap will result in the sensor clipping through or pushing to the other side same with explosives.

some doors allow you to pass through walls next to them when opening the door standing directly on the wall. It allows you get through areas that would normally require a lock pick or a code. 

I was just playing on the Riverside map, as I called for the elevator (pushed the button) by the dock. I waited 5 minutes, it never came. Didn't come down at all, either.