I did experience the folowing thing 2 times :
When sending, for example, 2 units to the training ground, 1 level 1, the other level 4.
On the first training the 2 units take one level (normal). the newly lvl 5 unit disapear (normal) and cannot be trained any more (normal).
Then I train the remaining unit 3 more times to bring it to lvl 5, this unit get as expected 12 ability points.
The problem comes from the previous unit that also earned 12 ability point when it should only have earned 3 (only went up by one lvl).
Happend at Dagbor training ground, but I assume it's everywhere the same.
Not that I mind the extra points but well ...