No one has died on Rockit, but a close Rockit TM has frequently talked about trains returning to the station with unconcsious or injured guests. Often blood has been all over the restraint. Not sure if this has to do with the closure, but it wouldn't surprise me.
The loop-crack theory is an interesting one, though the G-forces exerted on the top portion of the loop would seem minimal, as most of the energy is transfered forward on the incline, into the supports, and then downward into the declining supports.
The word on the TM street is mounting braces on the X-car are cracking, (not the loop, though that could be true, too), and that MS and Uni are working on a solution for that. TMs for Rockit are being outsourced to other attractions; full-time TMs are actually being cross-trained at these other attractions, which suggests that these employees are being re-assigned, somewhat permenantly.