We were recently in Tasmania for a holiday and hired a car rather than relying on my dad to drive us everywhere, which meant that a lot of navigation was done via Google and Apple Maps (not sure if Apple Maps being rubbish is still a thing, but there was no appreciable difference between the two in a week's worth of driving everywhere by GPS directions, with the exception of the roundabout stuff below, and Google completely failing at returning us to the airport, which was fine because our plane was delayed by almost two hours anyway).
Now assuming that you're not familiar with Tasmania, it's a small state with lots of mountains and terrible cell reception. This means that the data connection on the phone dropped out several times along most of our trips.
Usually what this results in is the helpful voice reverting to a "in 100 metres turn left" instead of "in 100 metres turn left onto towards " or similar. Instead (and I mainly remember this happening with Google Maps) we got several phantom roundabouts. We would be driving through the countryside without a roundabout in sight, and Google would chirpily inform us that at the upcoming roundabout, take the second exit. This happened several times, interspersed with the actual directions to the location which we were heading to.