Odd AlignOrientation Interaction

Hi, and thanks for reading in advance. I created a simple raft floating on a fake ‘ocean’ plane using an AlignOrientation and a PlaneConstraint. However, this happens:

No idea why. Only know that turning off the AlignOrientation stops it from happening. Anything I can do to nullify this odd behavior?

Repro File:
boat_test.rbxl (58.9 KB)