Timeline events appearing in random order and room history not loading

### Steps to reproduce

Not easily reproducible, I saw it in !lPCpzTqvUEAAXpOVzt:fosdem.org which suffered from the spam attack

1. Don't check messages for a week
2. Go to room with only event activity (no messages)

### Outcome

#### What did you expect?
Timeline is in order and room history loading times take seconds, or in the worst case low number of minutes. I don't get pings in the room.

#### What happened instead?
Messages seem to be out of order and I had four notifications in that room since a week ago (shown red in left panel). Room history took more than an hour to load past that point.


### Operating system

_No response_

### Browser information

Chromium 98.0.4758.80 (Official Build) Arch Linux (64-bit)

### URL for webapp

develop.element.io

### Application version

Element version: fa64d65e6e53-react-1c3507bc117a-js-cfad8d361454 Olm version: 3.2.8

### Homeserver

_No response_

### Will you send logs?

Yes