Pushing unprocessed events back in order

We are currently appending unprocessed events back to the event loop. This causes mixing up the chronological order of events.

We have currently seen unforeseen bugs in the state machine due to things like this. We can reduce the probability of errors appear by mitigating such actions.

To my understanding it should be sufficient to prepend the unprocessed events to the event loop. This way we ensure chronological order.

## Acceptance criteria
- [ ] Events from the same chain are always in the proper order
- [ ] tests are written and done

Start by locating the event loop and state-machine code that appends unprocessed events, then trace how events from the same chain are queued and processed. Verify the ordering behavior with tests covering unprocessed events, and consider the work done when same-chain events remain chronological and the tests pass.

Written by the indexing model from the issue text.