I got this from my father, who was told about it by a mate of his who was present as an Australian POW of the Germans in WWII.
I don’t have dates or places.
Two German troop trains stop at a railway station where another train holding Allied POW’s has been shunted aside to let the troop trains through.
One train holds SS troops going west, apparently coming back from Russia.
The other holds Heer going east, presumably to Russia.
Serious friction develops between the Heer and SS.
It increases to the point that each German side starts to deploy into tactical positions with weapons ready to use, including setting up crewed machine guns.
Officers on both sides manage to defuse it.
When the troops are back on the trains, the SS and Heer officers then get into vigorous conflict, which ultimately stops without gunfire but after some physical conflict.
The German trains go their separate ways.
My father’s mate worked out after the war that it was probably a conflict arising from Heer realising that they were going to have to go into an area where the SS had been butchering Russians and that the Heer would bear the consequences of what the SS had done before the SS headed back to safety.