As requested, your log will provide the answer. However, just off the top of my head -- this looks very much like the behavior caused when there are no markers for the AI.
Those are what AI engineers use to get around - and there are several maps that have all the markers except an amphibious plan. There was some code to default the engineers thru to the LAND plan if there was no AMPHIBIOUS plan, but I'm not sure that's necessarily in place in the FAF version of Sorian.