IMHO, I think the radio issue arise whenever you are in a weak signal transition area. Try un-tick the RDS option in your idrive - FM - Option page and see whether it reduce the interruption.
We got multiple regional FM frequency broadcasting the same channel, one of RDS function is help to search for the stronger signal broadcast. When you are in area of overlapping, there radio will become a bit haywire as they are busy searching and switching.
e.g. My FM channel broadcasting their program at 101.8 around Klang area and 100.6 for adjacent states (N.S. and Perak) but in KL, their 100.6 signal sometime is stronger than the local 101.8, then the radio try to search and logon to the 100.6 causing the sudden interruption.