"Cannot reach homeserver" after homeserver restart

(Disclaimer: I am a Synapse admin and I am here describing a problem encountered by many of my users.)

### Description

When the used homeserver restarts (eg. when upgrading), element-desktop says that it cannot reach the homeserver (as expected), but keeps saying that even after the homeserver finished restarting (not expected).

Then, if the element-desktop user completely disconnects from the homeserver, and tries to log in once again, she now repeatedly get the error "cannot reach homeserver". Restarting element-destkop or the computer does not solve the problem.

If another client is used on the same computer (eg. element-web or Nheko), it works perfectly. In fact, all users of the homeserver who were not using Element did not even notice a problem.

**Workaround**: deleting `.config/Element` solves the problem.

### Steps to reproduce

- Connect to a homeserver with Element-desktop
- Have the homeserver restart
- Try to re-login into the homeserver with Element-desktop

The error "cannot reach homeserver" appears.

Logs being sent: no (I have to ask)

### Version information

- **Platform**: desktop
- **OS**: Ubuntu
- **Version**: 1.7.7