Issue retraining units recruitable as mercs.

[Krampus]

In my Boii campaign, I was able to retrain any of my units at a settlement:
a) where I could train said unit, provided the unit pool was full enough; or
b) located in a region where I could recruit said unit as a mercenary, provided that the merc pool was full enough

I expanded west into Gaul and east all the way to Byzantium, with no issues for any particular units.

In my Pontus campaign, for many units which are recruitable as mercs:
a) I often cannot retrain them in regions where they are recruitable, even if the merc pool is sufficiently full
b) I often cannot retrain them in settlements where I could train them, even if the unit pool is full enough
c) sometimes I'm in a settlement where I could recruit or train them, the unit pools are full, and I cannot retrain them

Units I've found affected include:
- merc hoplites (including when I have the "train merc hoplite" objective that allows me to train a single unit from factional govs)
- aorsi riders (trainable)
- skythian riders (trainable)
- uazali (trainable)
- kurepos
- raskumenazi (trainable)

Units I've found not affected
- galatian raiders
- anatolian units, except for light cav (medium cav not affected)

What leads me to believe that this is a bug is that it's inconsistent for the affected units:
- sometimes the unit doesn't show up in the retrain window at all
- sometimes it does show up, but it says that the pool is empty (even when it's not)
- every once in a while it will let me retrain the unit, but if I remove the unit from the queue it doesn't allow me to add it back

Anyone have any insight on this? Thanks again, guys.