I can report (happily!) that upgrading the firmware on my Popp ZB-Stick to version 6.7.0 seems to have fixed this issue (GitHub - Elelabs/elelabs-zigbee-ezsp-utility: Elelabs Zigbee EZSP Utility to perform firmware update on a range of Elelabs EZSP products as well as other generic EZSP adapters.)
