Do not be so sure, Zigbee is extremely sensitive to interference, which is why you for example should not use the Zigbee Coordinator in USB 3.0 port or even close to USB 3.0 devices, again, do read:
Only other suggestion is to try performing a full factory reset and re-pair the SPLZB-131 device again, (know that you have already done that but doing that action should normally resolve any device feature discovery issues which show similar symptoms if the device feature discovery failed but still paired).
Next step is to enable debug logging and then open a new issue to Home Assistant core repository to get those debug logs analyzed (as the component for the zha integration is in that repo). See:
https://www.home-assistant.io/integrations/zha#debug-logging
and
https://www.home-assistant.io/integrations/zha#reporting-issues
If the device is using a ZHA Device Handler (a.k.a. a “quirk”) then could be there a bug in that quirk, or if device is not using a quirk then could be it needs a custom quirk (in ZHA Device Handlers repo), see:
https://www.home-assistant.io/integrations/zha#how-to-add-support-for-new-and-unsupported-devices
For reference; no one seems to have reported any known issues to these community databases:
https://www.zigbee2mqtt.io/devices/SPLZB-131.html
https://zigbee.blakadder.com/Develco_SPLZB-131.html
https://dresden-elektronik.github.io/deconz-rest-doc/devices/develco/splzb-131_smart_plug/
PS: Also suggest that you update your original topic of this thread to include the brand and device model in the subject, like for example: “Develco Smart Plug Mini SPLZB-131 connection problem”