read receipts sometimes don't have the correct avatar after initial sync

### Steps to reproduce

1. have a test room ready with multiple read receipts in the timeline view
2. switch to a different room
3. press "Clear cache and reload"
4. switch back to your test room

### Outcome

#### What did you expect?
I'd expect that all read receipts are showed.

#### What happened instead?
Some read receipts show the default avatar instead of an image.

### Operating system

Arch Linux

### Application version

Element version: 1.11.10 Olm version: 3.2.12

### How did you install the app?

_No response_

### Homeserver

imninja.net

### Will you send logs?

Yes