Bribed 'em, but can't use 'em?

[bamff]

What you want to do is to move the entire stack into garrison (if possible, ie allowed by the fort type sizewise). Then you can select single units from the stack again.

Interesting - I will be sure to give that a go when next I encounter this odd issue. Many thanks for the tip!

My own view is that this is some sort of bug, but I cannot work out what might be the cause. It seems to most often occur when bribing one stack in a province, then losing (or withdrawing from the ensuing battle with other units in that province). Perhaps the combination of the stack being "locked" while changing allegiance, and then "locked" again when ransomed back causes it to remain locked? As I said, after waiting out both lock events, I am then able to move the entire stack around to wherever I want, I just can't pull individual units out of it....

Anyways, I shall employ the "Bondovic Gambit" next time...