ESM Rule multiple firing

So I have a weird problem.

I have a standard rule that correlates 3 different events. It generally works fine, however for some events it starts firing multiple (2-4) times without a reason. 

I have checked and each rule event correlates same base events (same eventIDs, same endTime, etc). Each rule event has same time, same aggregation fields, and differ only in eventId

The rule is configured to run Set Event Field Action on every event and has matching time and aggregation time set for 30 secs. 

Does anyone now a way to troubleshoot this behavior.