Are you saying that the 36 is OK as far into the reel as the 24 and then gets difficult or does the 36 start to have problems much nearer the start?

Clearly the 24 doesn't go as far into the centre of the reel once it has been loaded so if problems start with the 36 after that point then it suggests that the "sticky parts of the reel may be nearer the centre which the 24 never touches.

Have a good look at the reel, check for nicks or any roughness in it, thoroughly clean it with a toothbrush and use Dr Croubie's idea. It has to be the reel. There is nothing intrinsically different between the same make of film whether it is 24 or 36 frame as far as I know

pentaxuser