Unit should be able to rout away. At the very least low crawl one hex down the road.
No other Russian units on the board... Pinned units cannot interdict.. can they?
The closest "cover" in movement factors (adjacent) are at maximum stacking capacity... that shouldn't force the unit to be eliminated. It has 6MF and could easily reach distant covering terrain.
I had the same happen with the Americans on the Makino Atoll scenario. There were no enemy in sight behind the unit, just lost enemy support weapons. It was crowded, similar to the above picture.