SUMMARY
There are two methods of changing the repeat behaviour of Elisa: you can click the button to cycle through Playlist, One and None; or you can click-and-hold to select the play mode from a drop-down menu.

If you don't use the drop-down menu at all, just toggling by clicking the button, the three modes work as expected. If you choose the play mode from the drop-down menu, the play mode you selected will be active.

However, after choosing from the drop-down menu, the button will no longer reflect the play mode you selected. Changing the play mode by toggling the button no longer works, and the play mode the button displays doesn't reflect the mode selected from the drop-down menu.

SOFTWARE/OS VERSIONS
Operating System: SteamOS 3.4.6
KDE Plasma Version: 5.26.1
KDE Frameworks Version: 5.99.0
Qt Version: 5.15.6
Kernel Version: 5.13.0-valve36-1-neptune (64-bit)
Graphics Platform: X11
Processors: 8 × AMD Custom APU 0405
Memory: 14.5 GiB of RAM
Graphics Processor: AMD Custom GPU 0405
Manufacturer: Valve
Product Name: Jupiter
System Version: 1