Unable to change RGB light colour since latest OS/Supervisior upgrade

Configuration
1

Since upgrading to core-2021.6.6 and supervisor-2021.06.3 on a Pi4 I now have a weird problem with RGB lights running tasmota via MQTT.

When I try to change the colour of a light, it briefly flashes the the chosen colour and then returns to white. Seems to have started happening for all my RGB lights???

I tried:

  1. Removing tasmota DevGroups
  2. Removing light groups from configuration.yaml
  3. Setting the colour for a single lamp
  4. Removing all scenes and automatons related to the lamps.

But I can no longer choose colours. Nothing I do fixes the problem.

I can:

  1. Still turn the lights on/off just fine.
  2. Set the light colour directly from tasmota.

What could I be doing wrong?