Boat circles back to hit waypoint, sometimes gets stuck in circle

I have a PixHawk set up to control a 12-foot boat with a tiller-driven outboard motor. In auto mode it usually works great but will sometimes act as though it missed a waypoint and perform a hard 360 to hit it. Rarely it will even get stuck in a loop around the waypoint and never straighten itself out.

I’ve messed with the navigation tuning parameters extensively but haven’t been able to find something that works consistently. I’ll sometimes be able to get it tuned well, but then the next time I set up the system it will have the same problems.

I’ve increased waypoint radius with mixed results, thinking that it would make the targets bigger.

Is there a way to make the autopilot understand that once it’s passed the waypoint, even if it wasn’t perfectly spot on, to mark it as complete and aim for the next? Or is there some tuning parameter that I should take another look at?