I can not comment on the MT4 default, as Zorro has no broker default. But if the FXCM API problem happened with the beta as well, it seems to be unrelated to the API version. I also heard from FXCM that they can not confirm such problems, neither with this nor with the previous beta.

Maybe the continuing FXCM problem is in fact an issue of your PC? Do you have the possibility to test on a different system?

Also, can you post the diag.txt from the situation when Zorro hung? Maybe we can then see which API function it was and forward the info to FXCM.