Some the basic non-clan skills for units in my army which were previously bought and unlocked with skill points are now locked.

For some reason the cost associated with buying those skills remains. So a good chunk of my army costs more than it actually should, by about 100 gold per guy.

I wouldn't care so much if it didn't also affect hero units, which cannot simply be deleted and re leveled. Or if when a skill was lost, the cost of the unit was changed to reflect this.

How to fix?