SUMMARY
When you open the Application Launcher and type with the keyboard to search for something, you expect the first item in the list to be highlighted, so that you can press Enter to get what you are looking for.
However, under certain conditions (see below), the highlighted item will not be the first, even if you didn't move the mouse, which will make you open the wrong app.

STEPS TO REPRODUCE
1. Open the Application Launcher
2. Type on the keyboard to search for something
3. Move the cursor to an item that isn't the first
4. Press the hotkey to close the Application Launcher
5. Open the Application Launcher again, and type with the keyboard again

OBSERVED RESULT
What happens depends on where the cursor is right now:
- If you moved the cursor is out of the way, then the Nth item will be highlighted, where N depends on which item was highlighted when you closed the Application Launcher before.
- If the cursor is in the launcher, then it will select the item over which it hovers, even if you haven't moved it.

(This doesn't always happen, it's a bit inconsistent. It seems to happen more often when there is no application open on the virtual desktop, and when the Application Launcher is opened (the first time) by clicking on it, instead of using a hotkey).

EXPECTED RESULT
If you don't move the cursor, the highlighted item is always the first on the list.

SOFTWARE/OS VERSIONS
Linux/KDE Plasma: NixOS Unstable
(available in About System)
KDE Plasma Version: 5.27.3
KDE Frameworks Version: 5.104.0
Qt Version: 5.15.8