I dont know is it bug or not.
When Soviets begin to receive reinforcements from 2nd turn there are rifle/support squads in the Rifle divisions have much less exp than others squads in these units.
For example, 2nd turn - 3 new RD around Moscow:
245 RD(morale 40) - rifle squads - 16 exp, support - 16, others - 28
242 RD(morale 38) - rifle squads - 19 exp, support - 13, others - 27
248 RD(morale 40) - rifle squads - 19 exp, support - 12, others - 28
New Rifle Brigade around Leningrad does not have similar problem.
New Cavalry Division around Odessa looks ok too.
Next turn and same things continues:
4 Moscow PM RD(morale 40) - rifle squads - 11 exp, support -19, others - 28.
New Cavalry on the south looks ok again.
So, why are these Rifle divisions so special?
So your question is why are certain Divisions experience level so low? Is that the question that you are looking to be answered?
“If you teach a man anything, he will never learn.”;