Have you tried to reset the SUM, and if still not enough, the BTS ?
In your traces, can’t you see any system information message “SI5” when in idle mode ? Those messages are listing all the “reselection” neighbours.
If these messages are
2/ not broadcasted
then the SUM is probably faulty.
If the messages contain coherent data (BCCH of neighbours), then it is your MS that is faulty.
Can you see some neighbours, or none at all, in idle mode ? Is it related the the freq band of the neighbours ?