BUG: Wrong windowlet when hovering over a toolbar icon (very intermittent)
Unfortunately, I cannot reproduce that at will, but observed many times with 1.16b and now 1.18b (skipped 1.17b). Hovering over a taskbar button often opens the windowlet card of the program next to it. The issue fixes itself with any program starting or closing. For example, opening the snap tool, which added its icon to the taskbar, sorted the order out.
I'll use any suggestions to narrow it down, but I see no pattern so far.
In the shot below, the only open programs are Notepad++, Slack and two windows of Firefox (they dyed the firefox' fur blue in the Developer Ed.). Hovering over Slack shows Notepad++ card, as pictured; Notepad++ has no card at all, and Firefox shows two windowlet cards for each of its windows as expected.
The Slack icon has a solid highlight rectangle of a very slightly brighter color, indicating hover. It's hard to note on the picture w/o magnification. This is where I rested the mouse pointer. Seems that the icon that is hovered over is detected correctly, but the window card that is popping up is wrong.
The screenshot was scaled 2:1 to compensate for the 200% display scaling. The Start button was immediately to the left to the Edge pin.

Update: Apparently, the Slack window is minimized, and has been since the notebook was brought up from sleep. Slack windowlet card has a border with only a window title, but its client area is all black. I just realized I didn't open it since opening the lid, and was only using FF and took notes in Notepad++, switching between the two using keyboard shortcuts. May be a clue?

Configuration
- OS: Windows 22000.556, x64
- Start11 1.18b in Windows 10 mode with Start11 toolbar enhancement enabled.
- HP Spectre 360 16" notebook with Intel XeLP on-package GPU (Gen11, Tiger Lake H), driver 30.0.100.9864.
- Single display (notebook's own panel), 3840×2400 native, with 200% "enhanced" scaling (the default, as opposed to "legacy" 8.1-compatible scaling, going by the name "Custom scaling" in Windows 10 and 11 System/Display options).
- Generally, Start11 is set up to retain Windows 10 look and functionality, except Windows 11 search is used. In particular, the toolbar is left-aligned.
- Taskbar icon behavior is set to "Always merge."