Steps to reproduce: 

1. Create a long line of blue ice facing west-east
2. Place a boat facing west and travel forwards

Observed result:
The boat will not successfully place due west, but slightly off to one side or the other. This does not happen for any other direction. You will end up falling off the line of ice going west, but not going east (if you place the boat correctly).

Expected result:
The boat successfully places due west.