Problem e1 + sip trunk

Hi there!

we are having an ocassional problem.
We have the following architecture:

2 Freepbx through a sip trunk: "A"y “B”.
Freepbx “A” has a E1 trunk.

Extensions registered in A make PSTN calls through a sip trunk with B.
Ocassionally the calls stop to go through.

Following I pasted the difference between a correct call and a failed call in the logs (this appears in the correct call but not in the failed call):
[Dec 7 16:25:05] VERBOSE[22980] app_dial.c: – DAHDI/4-1 is proceeding passing it to SIP/To_FSR-00003a45
[Dec 7 16:25:05] VERBOSE[22980] app_dial.c: – DAHDI/4-1 is ringing
[Dec 7 16:25:13] VERBOSE[3081] chan_dahdi.c: – Accepting call from ‘99250147’ to ‘9012929’ on channel 0/17, span 1

could this mean a problem wtih the E1?

THANKS A LOT!!!