Hello Stijn,
Looks like we have a missing Filtered Properties list in the v5.0.0 MQTT Engine module. I’ve made an issue for my Dev. Team to address this for the next release.
BTW: If you load v5.0.1 Engine module over v5.0.0 the Filtered Properties will still be empty. You must copy/paste from MQTT Transmission (Transmitter config) those Filtered Properties over to MQTT Engine General Settings and Save. Do this either before or after your upgrade(s).
Dan