Are you sure you have a 104? Because the 104 carries a7750 without the chrono module. There is no stem release screw on an 7750 so the chance of the stem comming loose would be next to impossible in that case.
It could be a small thing like a loose screw jamming something. Crack open the case back if you can and see what is going on. Try a big ball of sticky duck tape. That will do the trick unscrewing the back as most of the time they do not screw it on properly form the factory anyway.....