Strange bitcoind callback problem

[Gimmoroy]

Callbacks handled with shell script. System: Deb7 / 64.

bitcoind 12.1

It send callbacks a strange way:

cb1 (0 conf)
cb1 (1 conf)
cb1  ------  ?

cb2 (1 conf)

cb3
cb3
cb3

cb4 (0)
cb4 (1)

cb5 (1)

cb6 (1)

cb7 (1)

cb8 (1)

I.e sometimes it send one or three callbacks per transaction.

This generate problems for my system.
Is it some bug in bitcoind or may be bad settings?

System working about 6 month, but I saw this just a few days ago....