I already opened a lot of them but you won't like my advice To view images REGISTER or LOGIN for full access.
There's a gap on both sides of the aluminum housing. Slide a saw inside these gaps an saw in for 2mm, the housing can plied open with a flat screwdriver after the screws that hold the FETs are removed. The black gum is really soft and can be nibbeled off down to the parts you need to work/measure on (I use a filed toothbrush handle for that, black leftovers can be brushed away with a rough toothbrush like the ones you get on long flights from airlines) Be careful, SMD components don't take much stress to be damaged! Check the FETs and when you find ones with continuity also check its gate driver IC. I soldered out all my FETs on a damaged ESC and soldered in beefy cables to connect a external FET Module to be able to use 450A 90V FETs I have laying around from an old forklift. (I'm working on a speedmod that'll use 2 BLDCs, 2 modded ESCs, 2 batteries with modded shunts, and a horn instead of the tiny bell) I hobe to get 60-70kph out of this Frankenstein
I don't do magic, I do sience! One takes brains the other dark eyeliner!