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SUMMARY
When trying to pause/play media playing in background while the screen is locked, you sometimes have to press the button twice to work. Trying this via my bluetooth headphones, confirmed to be the issue with different headphones and only in Plasma.
When observing the locked screen, it seems that the lock screen has to be in the "enter password" state to work 100% of the time; otherwise pressing the buttons in the "time widget" state causes the lock screen to reveal the password prompt, as you would click the mouse/press enter.

STEPS TO REPRODUCE
1. Connect bluetooth headphones with play/pause button
2. Play audio (e.g. YouTube video in Firefox)
3. Lock the screen
4. Try to press the play/pause button on headphones while the lock screen is in its idle state.

OBSERVED RESULT
Instead of playing/pausing the audio, the lock screen shows the prompt to enter the password

EXPECTED RESULT
Played audio pauses/resumes playing.

SOFTWARE/OS VERSIONS
Operating System: Arch Linux 
KDE Plasma Version: 6.3.1
KDE Frameworks Version: 6.11.0
Qt Version: 6.8.2
Kernel Version: 6.13.2-zen1-1-zen (64-bit)
Graphics Platform: Wayland
Processors: 12 × 13th Gen Intel® Core™ i5-13420H
Memory: 15,3 GiB of RAM
Graphics Processor 1: Mesa Intel® Graphics
Graphics Processor 2: llvmpipe
Manufacturer: LENOVO
Product Name: 82XV
System Version: LOQ 15IRH8

ADDITIONAL INFORMATION