I bought a tape (From Here To Eternally by The Spinners) but every time I try to play it in either my portable player or tape deck it seems to prematurely think it's ended. I have tried rewinding it / forwarding it because a google result from this forum said to do so. It's a type 1 tape and there doesn't seem to be any screws if opening it up is needed
Since it's doing it in two different decks I'd suspect the tape is requiring too much force to get to the end and it's triggering the STOP. It could be a few different reasons, Coke dried on the tape, the plastic hub is damaged and doesn't turn smooth, the cassette case has heat damage or other similar factors. You might be able to FF/REW it to working condition after a few times or there might be some "lube" you can put on the parts. Luckily it's the tape and not the machines.
There was a video on YouTube about relubricating cassettes. Sorry I didn't make a note of it at the time.