Dysfunctional action box

[Rusty Nail]

I have had to abort three games due to this problem. In the action box at lower right, the box "locks" upon a particular unit (explorer in the example) and writes "unit is out of moves"- There is no moving on to a new unit if I click on the right arrow. If a new unit is then selected (combat rover in the example), the box remains unchanged except for the correct icon in the lower left. There are no action options available for the combat rover (or any other unmoved unit I select), forcing me to terminate the game. This has happened three times now in the middle of games, the most recent being after about 95 turns where everything up to then was normal.

Any suggested explanations? I am using several mods. which could be conflicting, but then why first after 90 turns?