My two-cents worth,
I've had problems with the 100D cartridges as well, on many different types of cameras. Especially nearing the end of a roll, the cartridge will often slow or stop. I've also sometimes been able to actually hear/feel the tension of the film in the cartridge winding unevenly in terms of speed.
The 100D stock cartridges seem to be made of a lighter plastic than the old 64T. Perhaps that is part of the issue.
I can only say that I've definitely had issues with this stock, and it's been very frustrating.
Good luck.