SOLVED: Aeotec Z-Wave Communications Errors

For the record, running on an RPi, I seem to have solved my Communication Errors problem by putting the Aeotec Gen5 Controller (ZW090), communicating with an Aeotec Smart Switch 6 (ZW110) on an USB extension cable and moving it away from the RPi. Which is actual a stack of assorted RPis and other SBCs.

Hopefully someone else will find this useful.

This is a known electrical issue with the older Gen5 sticks and the Raspberry Pi 4. Inserting a USB hub (or in your case, an extension cable) in between prevents the RPi4 from rejecting the Gen5 stick. Glad you got it worked out.