See post 1 for new version 2.1
This was due to a bad coordinate in both Canal nav files.
I had intended to run the boat close to shore after exit of canal as a joke
My error was that this might be funny first time, but not every time.
If boat is at extreme speed it may be too close.
I also repeated the coordinate in the inbound nav file - I did not intend to do this.
V2.1 removes this bad coordinate from both.
Sorry everyone