Mine was collecting dust as one of the newer, 'defective' models, and I took it out and realized some of the issues that have been raised have become blessings in disguise.
The cause for the field lock issue where it freezes up and restarts I do not believe is a technical fault. Frame synchronizers are used in many other situations besides tape. The root of the device's evil apparently stems from no stabilization compensation. It cannot handle vertical jitter at all, which typically and almost always where I have seen an issue. I am wondering if this device was designed with tape in mind at all.
This makes it a poor candidate for personal tapes, however, I have been doing a lot of commercial stuff lately and realized that with having more than one copy of the same tape, this issue actually marks the bad spots so it is easy to find sections to insert from a different source.
My two cents.