I think I know the answer already.
I have a cordless PNI traveller. it has served me well but is soon to be retired, replaced by an STI from Roy.
As of late it will alert to an LEO on K band, suddenly switch to Ka band for a while, and then back to K. (FYI they use both bands here so it can be confusing)
I doubt the cop is running both bands. I suspect it has gone out of tune.
Detection range is still good.