Hey,
Once again I see some random flickering similar to the reported one from a year ago. Here's a video for reference:
https://youtu.be/_JTSyRsTVWs

Hmm maybe there are more situations now with healthdirty flag being set now by Blizzard or other situations I must hook where they recolor border/health (below is just latest PTR blizzard ui script) does it happen only in retail or classic/cata also?

https://github.com/tomrus88/BlizzardInterfaceCode/blob/50f87b1505bac3ba0d4e185632eccab0a34f2043/Interface/AddOns/Blizzard_UnitFrame/Mainline/CompactUnitFrame.lua

Also do you have a screenshot from the addon options screen? Maybe that helps isolate where the bug is.

It was "ResetFrame too often #37"

Now the flickering seems to happen in longer intervals but it's still makes it unplayable.

Can you remember what issue number (under closed) it was? And the latest version you know since with the problem not there?

I remember Retail wow forced me to slightly delay color updating when "color border only" was enabled since default Blizzard UI scripts otherwise would override my colors shortly after, maybe that delay also happens without "color border only" enabled.

I know that since you fixed the issue back then it worked perfectly fine untill the end of dragonflight. I remember it worked just fine in the last season. This bug occurs since I resubbed to the new expansion.

Here's the screenshot of the add-on options. As for your question about classic/cata, I have no clue as I am retail only player.