When Russia invaded Ukraine, it became super obvious that their conscript soldiers are mostly untrained, poorly disciplined, have terrible morale and generally suck as soldiers. Their contract soldiers are much better trained, and they're mostly volunteers backed with some veterans who imparted at least some skills (Russian units are expected to train the recruits that arrive themselves).

As a result, Russia deployed their skilled soldiers in the areas of heavier fighting, which is a sensible choice. Attacking is a lot harder than sitting in a trench for a few years, after all. In ye olde days of WW1, these conscripts would have been called fortress troops, not trained to attack, only to defend their fixed position.

But Russia also didn't do that. Their border troop conscripts were, as with the original invasion, mostly shit. And if you pour shit into solid concrete fortifications, it's still going to drip out when you shake it, and that's exactly what happened. Again. For the third time this war.

So Russia can either pull their contract "volunteers" from the front to sit on the border, meaning they can't attack as well, or they can start losing troops and land to these kinds of attacks. Either way, sucks to be them, and Ukraine either gets a softer home front, a big chunk of Russia, or both.