I mean it's possible that it could have happened, but I feel like if you're going to make claims like this, there's a pretty high threshold of evidence required.
There's approximately as much evidence for Russian election fraud as there was for the 2020 US election: that is to say, some numerical anomalies, and poll workers acting strangely, with a few unlikely coincidences, but nothing that reaches the bar of hard evidence.
But the same people dismissing these claims in the US last year on the basis of "no evidence" are screaming positive affirmations about the same thing in Russia.
People are making affirmative claims of fraud on the basis of political priors in both cases, not actual evidence on hand.