Okay short version: IT IS WORKING!!!
Longer story:
Sunday
Updated domoticz to domoticz beta for synology
Updated zigate plugin to beta (checout beta/git pull)
errors all the time and at the end I had 21 routers in my diagram
2019-07-17 13:04:58.447 Error: (Zigate) retreiveTimeOut_Motion - Database error: database disk image is malformed
2019-07-17 13:04:58.447 Error: (Zigate) 'onHeartbeat' failed 'TypeError':'unorderable types: NoneType() > int()'.
2019-07-17 13:04:58.477 Error: (Zigate) ----> Line 744 in '/usr/local/domoticz/var/plugins/Zigate/plugin.py', function onHeartbeat
2019-07-17 13:04:58.477 Error: (Zigate) ----> Line 607 in '/usr/local/domoticz/var/plugins/Zigate/plugin.py', function onHeartbeat
2019-07-17 13:04:58.477 Error: (Zigate) ----> Line 1327 in '/usr/local/domoticz/var/plugins/Zigate/Modules/domoticz.py', function ResetDevice
erased memory zigate and added my normal devices. I left my house for a walk. Later that day I switched back to stable channel to be sure it would work the next few days. Did a last try to add the vibration sensor and it popped up in domoticz.
no problems the next days and today I had time to test if the router is working. And it does. No errors, no problems. It is recognised as a router and a switch. I can test the connection 2 ways by domoticz and the hardware button.
thank you for your help!