You're not using the latest version of the tweaerk - according to the screenshot, you're using v5.10. Please update to the latest version.

Unfortunately, I can't think of any explanation for this except for the things I already mentioned.

It’s difficult for me to investigate the problem without being able to reproduce it. We can try the following: here are three builds, each with some of the code removed. You can try them all, and report back which ones of the three versions cause the problem. Then I’ll focus on the part which causes the problem, and perhaps will send more builds more focused changes. Hopefully it will help us narrow it down to the root cause.

In this case, perhaps it's related to this problem:

https://tweaker.userecho.com/132-icons-loading-in-taskbar-buttons-somteimes-is-incorrect

Do you experience it when the tweaker is not running? If not, do you see the problem if you turn off all of the tweaker's options? Can you try and find out which option causes the problem?

According to your Firefox icon which is cut off a bit, my guess is that you're using the no_width_limit advanced option, and you made your taskbar too narrow. Unlock it and enlarge it just a little bit, so that the icons are not cut off. Let me know if that fixes the problem.

Fixed in v5.11.3.

The honest answer is that it's unlikely to be added in the near future. It's not a common feature request, and I have things which are of a higher priority, such as support for Windows 11.

No, currently there's no such setting in the tweaker.

Please see the newly released blog post:
7+ Taskbar Tweaker and a first look at Windows 11

I do plan to look at it when I have some spare time. I can't tell when exactly.

Hello,

I haven't looked at Windows 11 yet. I plan to look at it eventually, once it's more mature. The "stop apps from customizing the taskbar" item shouldn't be relevant for 7+ Taskbar Tweaker, since it's not using means that are provided by Windows for customization.