Chosen Solution
I just found an old Microcassette recorder and it worked at first, but after awhile they stopped working and now when I rewind it makes a buzzing noise. Also the little switch on the side has become loose and I can’t seem to get it to stay in one spot.
@flamma sounds lik you are having issues with the drive belt. Use these guides to check it out. you will have to unsolder the main board to get to the mechanism deck that includes the motor and the drive belt. Once you have the recorder open, post some images of what you see with your question. Use this guide for that. It will allow us to see what you see.
