Dave, there is a possibility we have set one of the ESC parameters wrong, perhaps the battery type is set to LiPo instead of NICb/NiMH or the cutoff voltage is set incorrect.
I reckon if we fully recalibrate the ESC now that we have the correct instructions your problem may well go away.
There is a possibility we will be flying Saturday or Sunday but if not bring it to sailing Saturday & we can have a look at the settings.