FLM03 MQTT broker crashes after new router


I have 3 Flukso's FLM03 in my network.
Since a couple of weeks the MQTT broker crashes constantly, after a couple of days the Flukso's are restarting them selves. Sometimes they are so badly crashed that even rebooting them remote via SSH is not possible.
It looks like this all starten when I replaced my router to a Unifi dream machine pro.
I have no clue what is going on.
Anybody some ideas ?