Tires.

This is coolbert:

Here is the explanation? There is a valid reason? 

From "Yahoo THE WEEK".

"How cheap Chinese tires might explain Russia's 'stalled' 40-mile-long military convoy in Ukraine"

NOT NECESSARILY CHEAP  TIRES ALONE! MUCH MORE THAN THAT!

[....]

"Trent Telenko, a retired Pentagon staff specialist and military history blogger, suggests another big reason may be Russia's tires, as he explained in a long, illustrated Twitter thread based on photos of deserted Russian Pantsir-S1 wheeled gun-missile systems and his own experience as a U.S. Army vehicle auditor. 'When you leave military truck tires in one place for months on end,' the sidewalls get brittle in the sun and fail like the tires on the Pantsir-SR, he wrote. 'No one exercised that vehicle for one year.'"

Pantsir mired with blown tire. Stuck in the mud of the rasputitsa and excessive efforts to extract the vehicle only exacerbating a situation with weakened tires? A wrecker needed to pull the Pantsir out of difficulty, you can ruin the engine, transmission and other tires by any other futile effort.

I have always been told keeping a vehicle of whatever type idle and sitting in one spot for a long time that portion of the tire hitting the pavement flattened with all the pressure and weight of the vehicle creates tire weakness and you are in greater danger of sustaining a flat. Use it or lose it is the well-known adage and admonition!

coolbert.