After contact with Athom and several different solutions I can tell that the following worked for me:
- Put your Homey in recovering mode
- Go to setup.athom.com to reinstall
- Reinstall through your browser, not by the Android or IOS app
- While the Homey is searching for updates, press the ALT button. Select ‘Download full update’
- Keep your user data
- Perform a FULL Zigbee reset otherwise the problem will come back after several hours.
EDIT: Athom would like to know how big the issue is, so please also send an email to support@athom.com
EDIT: Point 6 added as I had the same issue.
THIS IS MY SOLUTION and maybe won’t work in your specific situation. In that case, as mentioned before: contact Athom!