BS11 power problem

Hello All, Herr Thomas had raised up a discussion about problem with setting of BTS power attribute value. In connection with this question, I recall another problem which has occurred with one of my BTS's. It has a very strange behavior. Its output power is set to 2W. My measure device tells me that receive level at the desired channel is about -24 dBm after station boot-up. This value is very good, no other base station around shows better results. But right after the very first GSM call the receive level quickly jumps down to -70 or even -80 dBm, this value corresponds to 30mW of output power. BTS station still works and output power is still shown as 2W. This effect had been discovered with only one of my BTS stations, while other stations work well. Does it mean that it's a hardware problem? Has anyone discovered this problem earlier? Best Regards, Sergey.