Nad 6100 Cassette Deck plays a few seconds just fine then stops

Thanks in advance for any help. I just bought this and the head looks good and the rubber wheel thing spins and is nice. But, I tried 3 tales and each plays a few seconds and then the deck stops itself. When I pull the tape out, it has a tiny loop about 3/4 inch high that did not go into the rest of the shell like it should. I guess there is something that needs to make the tape wind up that is the issue. The sound is clean for the fee seconds and the unit is in great condition. Even came with the box. It is the 1988 version. I think there is only one belt in it and I am not scared to try to fix this. Please help if you can and advise me as to what I can do. I really like this new toy and am excited to get it working right. I won’t test anymore until I get some answers, but its behavior is consistent. Thanks in advance!