Dual 4500s. PFD is EFIS only and MFD is EFIS/EM.

I'm in phase one flight testing. About 30 minutes or so into every flight I've had the PFD (EFIS only) bring up a "Remote AHRS Failure" message. The MFD (EFIS/EM) continues to function just fine with no messages, but it loses GPS because the 430W is connected to the PFD. After shutting down post-flight, if I fire back up the PFD, MFD, ethernet hub, and airinc things are back to normal.

Any suggestions for trouble-shooting? It feels like an ethernet issue because it seems like the PFD is losing all communications with the MFD. Maybe a bad ethernet hub which fixes itself on power cycle?