Solved the re-connection problem by giving the MQTT broker a different and seperate IP-address, it was running on unraid´s main IP-address. Now testing for repeating relay activation, keeping fingers crossed. @Yveaux thx for your help.

Nice work @thedutch, thanks for reporting back. In case you need anything similar, https://www.mysensors.org/apidocs/group__RF24SettingGrpPub.html lists the co figuration options for the nrf24 radio.