Cassette play button/slide rstuck

Hi everyone, I'm new to cassettes and the culture surrounding it but recently I came across an old JVC play / record deck but whenever I tried to play something on it it would spin for a bit and soon it would stop and start to emit a high pitched noise. I tried fixing it but when I put it back together the play/rec slider was jammed up. I can't seem to find what caused it, if anyone knows anything about either of these problems I'd greatly appreciate the help.

edit: I'm not sure on the terminoligy, it's a handheld device, not a deck