It sounds like election workers are doing their job of screening for fraud, so good for them. They are investigating, some of the ballots might be legit, some not.

Why is it that Republicans assume if there is fraud (and evidence repeatedly shows it's very minimal) it's always in favor of the Democrats?

Part of the reason for that is that Donald
Trump has pushed this narrative ad nauseam and his weak minded MAGA cult believes all of his lies. Did the fraud just go away when he actually won the election. By the way MAGA, he only won one election, he lost the last one.