MT messages queue

Hi all,

I had a problem with bearerbox this morning and I don't see the source 
of the problem.
In fact all MT messages to SMPP smsc1 where queued and stored in file, 
but all messages to smsc2 and smsc3 were submitted correctely.
MO messages are received correctely from smsc1, smsc2 and smsc3.

When I look the log file, there is no ERROR message and enquire_link are 
sent/received correctely.

I restarted kannel then all stored MT messages  were sent to smsc1.

I don't understand why MT messages to smsc1 were queued?
and why they were sent immediately  after kannel restart?

Has someone experienced this phenomenon?


Regards
--
Djiby