Thank you very much Kaeno, it worked on the 3.5.0 version of it (3.5.3 is still bugged with the same error message even after replacing my json with the one you gave me) and I noticed that the scope I had on my AK disappeared, so that was definetely the issue here, but I'm sure that I played a few games with it before the crash.
I don't know why this problem came up, but it's fixed for now. Thank you to those who helped !