[cisco-voip] Upgraded UCCM and modem-relay stopped working

[Andrew Zerger]

I recent upgraded from 4.2.1 to 4.2.3, and on gateways where modem- 
passthrough was configured and working (14400 codec for faxes), it no  
longer is.

ATA devices which are plugged into fax machines now operate on g711,  
but the service is inconsistant, it had been in the past before modem  
passthrough was configured.

In the old version where 14400 was obtained, MTP was set on each  
gateway, after the upgrade, call-transfer and forward  for offnet  
calls stopped working, removing the MTP checkbox
fixed the problem, but now complaints about the fax being inconsistent  
are widespread.

What might be wrong here that is stopping offnet calls from working  
when MTP is checked?