1) Mannerheim as army commander: I am not able to create an army with Mannerheim as commander. Since he is the highest ranked commander the Southern White has that means NM penalties if I create an army with somebody else.
According to the tooltip you need an Army HQ, but you cannot build them in RUS! Building the Finish HQ replacement doesn't help, either.
2) Several recurring economic options don't work the second time around (i.e. in 1919):
- Decree partial mobilization (Red and Southern White)
- Recruit prisioners (Red and Southern White)
- Recruit DON Cossack general (that one has already been reported, I never receive them)
- Red cossacks recruited (Red, obviously)
- Restore Red Airforce
- Party Members join Army
This is really annoying since is further cripples the ressource supply. As concerns the Sibirian White, I have no idea (haven't had time to play that side long enough).
3) Replacement system: The Southern White periodically looses access to some of his subfactions: North-Western Whites (on rare occasions I can buy replacements most of the time that faction doesn't even appear on the replacement screen), Germans dissappear sometimes from the menu. I had the French dissappear for a few turns in 1918 once. And yes, I am aware that there are arrows to scroll through the subfactions.

On the other hand, some replacement options are useless: from mid summer 1919, the Southern White can train Komush replacements. Vice-versa, the Siberian White is able to train Southern White replacements.
4) In early August 1918: the third Japanese division arrives in the Far East according to an event message, however no troops appear. I looked up the event script ("evt_nam_Renforts_CMN_JapaneseInterventionB"); if I read it right, it is part of a cascade of three events that should remove red troops from Bikin and spawn the Japanese division instead. Can't find the error.
5) The last one is a question, not a possible bug: What exactly does the "Recognize Independances" diplomatic option do for the Southern White. I once tried it out but didn't gain anything during the next few turns. Is that huge NM hit worth anything?
Edit: Should have clarified, I am playing the Grand Campaign.