As I have an unusable situation anyway, next to ordering a HA box I decided to just start anew to test the Homey.
- Full software restore of 10.0.7 rc2
- Moved Wifi channels as far away as possible
- reset Homey zigbee, new channel as far away as possible from wifi
- added routers across the house slowly (~ 15)
- added end devices in the place of use
Within 2 days: it all falls apart again.
And to remind some of you: this same setup worked a few homey versions ago. Not the most stable and fast situation, but it worked.
So narrowing everything down, this is just a failed update from Athom. And before it goes into ‘it’s just you’ again, look at the increase in zigbee network problem topics here. And that’s while many heavy users already went to a separate zigbee network and many not having more than a few zigbee devices.