Any case that soviet soldiers killed their own commissars?

[Stiltzkin]

"Why Stalin's soldiers fought" by Roger R. Reese

Yes, Reese is a good scholar. The main thesis though was not just the ideological background but rather the life, death struggle in which the USSR found itself in. There were Hiwis, deserters (the USSR had the highest amount of them) the troops were already repressed by their own system but a German victory would have meant the annihilation of slavic civilization.

[ML59]

From Wikipedia: Documented and suspected fragging incidents totaled nearly nine hundred from 1969 to 1972. Fragging has not been as frequent since the Vietnam War ended.

Not the best source, nevertheless a starting point. Maybe others have a better source.