I've known about the problem with the index finger bending on its own for a long time, around 3 or 4 years. I believed the VRChat team would fix it, but they never did. I need to report this bug, which affects people using Valve Index controllers. For years, we thought our controllers were broken, leading us to replace them through SteamVR or buy new ones, but the issue is actually a bug in VRChat.
For those of us who are deaf and use sign language, this bug is particularly uncomfortable and causes miscommunication sometime.