SUMMARY Searching and pressing enter multiple times, in the Overview effect, before an application launches will open multiple instances of searched application. And possibly related, any application launched through the Overview effect doesn't have an opening window animation. STEPS TO REPRODUCE 1. Enable the Overview effect 2. Open the Overview and search for an unopen application 3. Press enter multiple times in rapid succession OBSERVED RESULT Multiple instances open and no opening window animation is played EXPECTED RESULT A single instance with an opening window animation SOFTWARE/OS VERSIONS Linux/KDE Plasma: Arch Linux KDE Plasma Version: 6.4.4 KDE Frameworks Version: 6.17.0 Qt Version: 6.9.1 ADDITIONAL INFORMATION On Wayland.
Can reproduce the multiple instance issue. It doesn't happen in KRunner itself or Kickoff, only Overview. I can't reproduce the lack of opening animation issue though. It's possible your opening animation is shorter than Overview's close animation. Either way, let's track that in another bug report, if you don't manage to trace it down to a configuration issue.
After some further testing it seems to be tied to the closing animation of Overview. Overview still takes in input during the closing animation, causing the multiple instances thing and, when searching for an unopen window, all the other open windows in that virtual desktop are hidden and when closing Overview brings the windows back abruptly which causes the opening window animation thing. Both problems are more noticeable when you turn the animation speed down.