hi,
without chaging anything in the system, your KPIs are getting good and bad “by themselves”.
Is there enough traffic on this BTS for you to be certain that the QoS Stats are based on sufficient amount of samples? If you have 10 calls per hour, then the random occurence of drops will have severe influence on your KPIs.
If you have enough traffic, then it is obviously a HW instability. It cannot be anything else.
Try changing the TRX, the combiner, the BTS, etc…
That’s just my 2cts… if anyone has another idea…