The new header causes high cpu usage

### Steps to reproduce

1. Where are you starting? What can you see?
2. What do you click?
3. More steps…

1) The issue started happening when the new header entered beta. If you opted out the cpu usage was normal.
2) Just switch bettween rooms -especially ones that have many users like matrix Hq

From what i read in the element web matrix channel it happens with many browsers and is independent of operating system. Many others faced the issue.

### Outcome

#### What did you expect?
Normal CPU usage
#### What happened instead?
HIgh CPU usage

### Operating system

Linux

### Browser information

Firefox

### URL for webapp

app.element.io

### Application version

.82 stable

### Homeserver

_No response_

### Will you send logs?

No