Disappearing custom relation events after restarting client or initial sync

### Steps to reproduce

When closing Element Web (I've tried app.element.io and develop.element.io) or clearing cache, the `m.notice` messages seem to disappear.

Here is a screenshot of an example ping test I just ran in the [#ping-no-synapse:maunium.net](https://matrix.to/#/#ping-no-synapse:maunium.net) room:


Then how the room looks after clearing the cache in client to perform an initial sync:


I've also tried using /devtools to show all hidden messages and there's simply no trace of these missing `m.notice` messages. I'm confident it's not a server issue as this behaviour doesn't occur in Element Android or other clients.

### Outcome

Expected outcome is that rooms would appear roughly the same after restarting client or clearing cache as they did beforehand.

### Operating system

Microsoft Windows 11 Pro 23H2 (22631.3235)

### Browser information

Microsoft Edge 122.0.2365.66 (Official build) (64-bit)

### URL for webapp

develop.element.io

### Application version

Element version: f01d69f90b98-react-942fabc5a8fe-js-7fee37680f33 Crypto version: Rust SDK 0.7.0 (b1918e9), Vodozemac 0.5.1

### Homeserver

doctoruwu.uk

### Will you send logs?

Yes