Eh around the time of the Wagner pullout from Bakmut there has been signs that there was a large amount of discontent between the mercenaries and the MOD. They had been throwing threats at each other along with rumors of shooting at each other at times.

Oddly enough on some more of the hypothetical and conspiratorial parts of the net possibilities like this have been discussed for weeks. It's just so odd to see this happen in real life.