Issues with encryption keys

### Steps to reproduce

In one of my DM, I have a strange behaviour, where I can't read messages, and I can't fetch them from other devices. Today I could read the first messages and reply but I couldn't read next messages from the other side. Apparently the other end can read my messages.

### Outcome

Being able to read the messages, but this is not working in this specific DM, on all devices * iOS, Android, Electron or Web).

I'm using a matrix.org account and the other party another homeserver.

### Operating system

_No response_

### Browser information

_No response_

### URL for webapp

_No response_

### Application version

_No response_

### Homeserver

_No response_

### Will you send logs?

Yes