Probably discount bullets from the lowest bidder.
Russian ammo can be quite cheap. And crap as well. The gasses from their powder formulation can be quite corrosive, and then the powder loads have been known to be a bit on the light side - less velocity = less kinetic energy,
Don’t buy Wolf and Bear ammo!
I generally use reloaded cartridges that I make up myself even in our eastern block firearms because they are less corrosive. But it is not the powder that causes the corrosive properties... it is the Berdan primers many of which leave corrosive salts in your gun.
The most likely explanation for poor performance from the cartridges used by the police in this instance is probably improper storage. If ammunition is not stored in cool dry locations its performance will suffer over time. I store all of our ammo in sealed containers with desiccants to absorb moisture from the air.
This may explain the difficulty you seem to be describing from surplus Eastern Block ammunition. I have never had any difficulty with Eastern Block ammunition that I removed myself from a sealed metal tin even when it was very old.