Hmm...I wonder if that's a clue. Come to think of it, when these bugs are occurring, if I'm looking at the map in general with no route established, my exact position seems to be a bit jumpy...almost like Apple Maps is having trouble pinpointing my exact location.
Now, I live in New York City. Cell coverage is nearly perfect everywhere. I'm seeing maximum strength signal bars as I drive, and I'm not experiencing any issues with Google Maps or Waze, so I don't think it's my phone. I'm still convinced (for now) that Apple is in high gear making improvements and updates to Apple Maps in the background, and it's occasionally causing these bugs for me. I can't imagine why else it would be "bad" for a week, work perfectly for a week, and then go bad again.