Totally agree here.
It’s always helpful to hear about shared experiences. I did the same thing when I set up this forum thread for people experiencing hand and arm or shoulder pain - it’s pretty helpful too:
For the problem of joints collapsing when you apply pressure - I’ve seen similar things in many many students. It seems common in beginning students as you’re asking these tiny parts of your fingers to do very labor-intensive work.
I’d try every and any technique alternative to try and find something that’s more comfortable for your hand. The classic perfect technique of one-finger-per-fret, bent last joint landing perfectly like an eagle claw on the string doesn’t work for everyone.
Having said that - keep coming back to it.
I had this experience on the upright - collapsing joints.
I kept practicing, and it got better. Just took a long long time.