[brian johnston] “Media100 themselves are useless!”
I think that saying something like this won´t help you much. And your problem definitely is not a general problem with Media 100, but with your deck setup and connections. So instead you should post a little bit more about the things you tried while “nothing has helped”, and about how your deck is hooked up.
If you try to acquire material from the deck into the system you should make sure that you only connect the Output from the deck (SDI, Component+audio or whatever you are using) to the Media 100 system. Set your deck to PB mode (no E/E). Make sure that you DO NOT feed e.g. a sync signal from Media 100 to the deck while trying to acquire (no out from Media 100 to your deck!!!), and make sure you don´t feed a video or audio signal from Media 100 to your deck. Then you definitely will not get into a feedback loop, which of course would irritate the Media 100 hardware and cause these relock sync problems you are seeing on entering play/acquire mode.