FAX SEND/RECIEVE PROBLEM

Question

We have a Centralized Call manager cluster That are running MGCP we have:
1. three VG224
2. two Voice gateway running (E1 PRI )
issue # 1
- when we send a fax from one fax that is connected to one VG224 to another that is connected to anothe VG224 failure occur.
issue # 2
-When we send fax to PSTN :
a-one fax can send and receive with no problem ( TOSHIBA)
b-another Fax that are connected to another VG224 can send but the receving sometime fail and sometime we have part of the fax received.(
the phone connected to the fax are working okay and we have a dial  tune.)
What I have tried:
1.Change the VG224.
2.Connect both fax on the same VG224 still have the same situation.
3.connect the fax that does not send or receive on the port of the working fax solve the problem work fine.
Note: I see some SLIP error under the controllerr interface and I notice that when I go out with line xxxx1607 it works fine whatever the port on the VG224 when I go out with xxxx1648 it failed knowing that the xxxx1607 is the line of the working fax and the xxxx1648 is the line of the failed fax.
- I have attache the Voice gate way and VG224 sample configuration.

Answer 1

If the calls only fail when going through the gateway with slip sec errors, then it probably the cause of the failures. Add "network-clock-se
lect 1 E1 0/0/0"
The VG224 configuration is also missing the commands to enable modem/fax passthrough.
Add the following,
voice service voip
fax protocol none
modem passthrough nse codec g711ulaw
For reference,
http://www.cisco.com/en/US/docs/ios/voice/fax/configuration/guide/vf_cfg_mdm_psthr_ps6441_TSD_Products_Configuration_Guide_Chapter.html