Ok perfect, thank you for sharing! This was my hunch, so thank you for confirming.
Here’s what I think is happening, but I may need you to test something for me.
Basically, the switch looks to be paired in S2 mode (zw: Ls2a) whereas your bulb is paired in S0 mode (zw: Ls). Unfortunately, if there are two different security levels, they cannot be associated.
What you used to be able to do up until a couple weeks ago was force the switch to pair in S0 mode (the switch has both S2 and S0 built in, whereas the bulb only has S0) by either not inputting the QR code or by hitting, “scan nearby” when pairing (instead of hitting QR Code).
However, based on this thread I completely forgot about, ST may have changed something:
I meant to send an email to the engineers at ST to see what happened.
Is there a way you can try unpairing and repairing your fan/light using the, “scan nearby” method? If it ever asks for a QR code, just either don’t input anything or back out and see if the switch still pairs?
What I believe is happening is you may have thought your switch and bulb was associated, but it actually wasn’t (due to the security mismatch) and when you physically dim smart bulbs it causes them to flicker as they can’t be dimmed manually (ie: they have to have the full 100% power).
Make sense? Sorry if I didn’t lol.