MAS username sync fails partially

### Steps to reproduce

1. Where are you starting? What can you see?
We use the latest element server suite version with helm and have MAS with keycloak configured.
When somebody logs out and logs in again, then certain user names dont have their username displayed but their full wellknown id. This is a bug as it should just show the user name. This does not happen for all users strangely.
This happens in the Browser as well in the Element Desktop Client.

### Outcome

#### What did you expect?

#### What happened instead?

### Operating system

Win 11

### Browser information

Brave and Element Chat for windows

### URL for webapp

_No response_

### Application version

element 1.11.105

### Homeserver

latest

### Will you send logs?

No