There are other places on the internet that describe it much better - but a lot of it sounds like it is down to "pad of death", a common problem with the series of camera you have inherited.

Welcome to APUG and happy shooting - if you are practical, you can replace the pad of death (and the light seals, since they have probably deteriorated) - I know Jon Goodman (a name that will come up time and time again) sells them and has an excellent reputation, so something to consider.