Navigation freezes

I live in San Diego and sometimes drive to places in Los Angeles. Sometimes on the way home the info on the upper right (freeway exits and turn offs) stop updating. The info below, which shows miles and ETA doesn't change.

The map sometimes works and other times it stays still. Sometimes if I touch the screen and then touch home I may see the current exits coming up, but it pops back after a couple of seconds to old info, or says "UNKNOWN ROAD" when I'm clearly on the freeway.

I haven't powered down and back up as I'm generally in a spot where an exit would be tricky or I really don't want to get off at that location. When I'm passing Disneyland going South it comes on again.

It doesn't happen going North and not in every location. I suspect that the LA area is cutting off signals that allows the Navigation System to update.

Has this happened to anyone else?