Zigbee odd route - leeds to unresponsive devices

Sounds like you may have too many Zigbee devices connected to Homey.

11 router device and 5 end device

That shouldn’t be a problem. Have you ever performed a Zigbee reset?

Yes, twice. After the first 5.x rc and after the update to 5.0.4 when problems started.
Do you think I should try it again?

I just now read that you’re using Osram devices. Those don’t always work well together with others, especially Aqara devices.

Also, if I understand correctly, your main issue seems to be that when turning on/off multiple devices at once, some devices don’t react. Is that correct? Because that’s been an issue with Homey for quite some time now and isn’t limited to Zigbee.

No, there are not several devices that switch on / off at the same time. There are different times and different scenarios on the different devices. So you think I should replace the osram units? Is it only with Homey that osram has problems?
I have a hue lamp. It seems like nothing meshes through it?

You can try and see if it works better without the Osram devices, but it’s not a guaranteed fix for your problems. Also, Zigbee devices make up their own mind on how they are routed, you (or Homey) cannot control it.