hi,
what are the stats for Idle Band measurements, per TRX?
if it is external interference located in the UL GSM band, the only way to properly fix it is to scan the area, fond which frequencies are impacted and what is the source.
Then shut it down.
The cowardly way is to find clean frequencies, knowing that the problem might be on all frequencies or that it can randomly appear anywhere.
Cheers
pix