Alexx,
I have the same problem with GSM NORTEL but in my cells appears and dissapears after some hours, it is not periodic or continuos.
T3101 was the counter I found is increased during the problems.
I realize the SDCCH seizures are almost the same as when there was no problem, but the SDCCH attempts almost doubled, creating SDCCH Assignment Failure Rate high.
Any other test you do? Can you explain the traces performed?