Lights flicker when pairing IKEA Vallhorn?

Configuration Zigbee
1

So I think my Zigbee network might have a poltergeist?

Trying to pair a Vallhorn sensor (already have 2 others on my network) but it’s not getting past “Configuring” stage. The sensor flashes somehow in the affirmative, and then my living room lights (on a Moes switch) start going wappy!!

See video…

And idea what’s going on?

2

For info, I have the proper IKEA batteries. Using Sonoff Dongle P.