App doesn't go into fullscreen correctly if it is maximized

[Puyo]

Plan

Premium

Country

Spain

Device

Desktop (Linux)

Operating System

Arch Linux (kernel 5.11.16-arch1-1) with X and KDE Plasma version 5.21.4 (using KWin for window management)

My Question or Issue

If the Spotify window is maximized on a display that isn't the primary display (i.e. 2nd monitor), going into fullscreen just shows a black screen. This does not happen if the window is not maximized, or if the window is maximized on the primary display. (spotify can go into fullscreen on the 2nd monitor, as long as the window isn't maximized)