I have Fuze+ rockboxed for more than 3 years. And no problems that you describe occure. Also while OF was a real nightmare, Fuze+ was stable even with OF. I freezes sometimes or restarts, but seldomly (once a month or so). Generaly every electronic device fails from time to time....
I guess your player is defective in some way. What comes in my mind, it might help to reformat the internal memory. Maybe that some of developers of this port would have some idea, what else to try or how the reformat should be done.