@1049 not quite sure what the real problem is but I suspect the following: your tape loop might be too tight. i can’t really tell by the image or video but your loop can be completely loose and should on no occasion be ever too tight. the tape being hard going makes your machine assume you arrived at the end of a regular cassette and stop.
in many cases the left turning wheel is only ever powered for rewinding anyway but I am not sure about this specific model of recorder. but generally one can assume that this is the case in most gear.
for playing tape loops, one does not need any of the turning wheels at all. the tape is usually moved by the pinch roller on the bottom right alone, whilst pressing on the capstan. you might need to adjust the pressure settings there if anything. even a regular cassette is primarily moved by the capstan/pinch roller. the turning wheel inside the cassette just winds your tape up and has not much to do with actually moving your tape forward. if you buy factory made endless cassettes only one, if any, of the turning wheels in the case ever engage with the winding mechanism and the tape is solely moved forward by the capstan/pinch roller (but perhaps kept tidy by one turning wheel if it’s a long loop).
not sure if this will help you trouble shooting but it might be something to look at if you didn’t do so already…….