Troubleshooting tips please - Tradfri Bulbs no longer switching, other Tradfri items still working

I run 3.3.0 Openhabian on a Pi . I have a Tradfri hub connected which operates two outlets (GPO) and 10 bulbs. Yesterday the bulbs stopped switching. The outlets are still switching.

Looking at Settings > Things, all the Tradfri items show as online. Using the OpenHAB UI controls, I can turn the power outlets on and off successfully. All the controls that operate bulb brightness and colour produce no response.

Using the Ikea Home Smart app, the bulbs all operate correctly.

Looking at the event log, when I turn the lamp brightness (bulb 5,6,7,8) to 100 in the openHAB UI, the logs report ‘received command’, ‘predicted to become’ and then ‘changed from 0 to 100’.

Activating the lamp from the Ikea app, I see the logs showing the ‘changed from’ events.

So as best as I can tell, openHAB all seems to be working correctly, no errors being reported, nothing showing as offline, just no response from the bulbs, only the outlets. So I don’t know where to look from here.

The bulbs ceased working on version 3.2.x As standard troubleshooting I did a reboot, figured there might have been some updates so updated and have now upgraded to 3.3.0. Given I was seeing the problem both sides of the upgrade I don’t think that’s relevant but mention it for completeness.

Appreciate any thoughts on where to look next. Thanks!