I may have just figured out what causes this bug to occur (the one I described in OP).
I just moved my troops between two towns on the same island (across land), accepted the currently longer travel times involved in doing so.
The pillage I sent right after moving those units had the travel time bug, same thing... Recall and resend reducing the actual travel time by a few minutes each time after initially stating it would take 24 minutes I got it down to 12 minutes, still not as quick as the 7 or so minutes I would expect to see (which I was getting from the other town on the island to the same target).
I am pretty certain I did exactly the same thing the first time I noticed this - moving units across land before sending the pillage.
So currently the way to mitigate this (I think) is to just avoid moving units over land - if you want to transfer between two towns on the same island then send via. boat to another island, and then back into the town you want - bit silly but I think this will work to at least avoid the bug until fixed.
I'd be curious to see if others notice the same, I haven't noticed these issues after stationing units across islands.
MH