I am experiencing an issue with call delivery on Android (Element X)

### Steps to reproduce

I am experiencing an issue with call delivery on Android (Element X).

Incoming calls (both video and audio) are sometimes not received, while message push notifications always arrive reliably. I have tested multiple notification setups, including standard FCM, a custom fork using a separate Sygnal server, and ntfy. I have also verified that all notification permissions and battery optimization / power-saving settings are correctly configured and disabled where required.

The behavior is inconsistent: in some cases, the phone can remain idle for an hour and an incoming call is delivered correctly; in other cases, after only 5 minutes of inactivity, call notifications stop arriving. This issue reproduces across multiple Android devices, not just a single phone model.

Network latency or connectivity issues can be ruled out — the problem does not appear to be related to network delays.

Has anyone encountered similar behavior on Android? Any insights into possible causes or workarounds would be greatly appreciated.

### Outcome

#### What did you expect?

#### What happened instead?

### Your phone model

_No response_

### Operating system version

_No response_

### Application version and app store

_No response_

### Homeserver

_No response_

### Will you send logs?

Yes

### Are you willing to provide a PR?

Yes