Kenny, I'm not sure if you're still following this thread, but I've got to say that compared to the AudioCodes MP124, the Grandstream GXW4224 is flipping brilliant.
I literally set up the device/MAC in FusionPBX, set up some test extensions, logged into the 4224, added the IP of the PBX, added extension/password to the FXS port. Done. It was 5 minutes before I was making inbound/outbound calls with this thing and I was shocked to say the least. I believe AudioCodes has cashed the last check it will ever receive from me.
** Also, I did some testing specifically with ports off-hook simultaneously and I could not recreate that issue you had with the ports failing to recycle and go back on-hook. Zero issues to report.