Keyboard media keys work on one user profile but not another?

Operating System: Debian GNU/Linux 10

KDE Plasma Version: 5.14.5

Qt Version: 5.11.3

KDE Frameworks Version: 5.54.0

Kernel Version: 5.4.0-0.bpo.4-amd64

The Stop, Previous, Play/Pause, and Forward keys have stopped working on my keyboard.

When I first started troubleshooting the issue, I tried remapping the keys in systems settings>shortcuts>global shortcuts>media controller but when I tried to set the various media keys as custom shortcuts, the last thing/ui button I clicked with the mouse would flash as if I’d clicked it, but nothing would actually happen.

I have a 1st gen Corsair K95 RGB (the version with 18 macro keys), and I use ckb-next to enable / control the keyboard’s functions / macro keys / lighting etc. I have tried disabling and even uninstalling ckb-next but it mad no difference. I’ve tried saving various different profiles to the K95 hardware itself but again, it made no difference. I’ve also tried flipping the hardware compatibility switch on the keyboard setting, which basically disables all the advanced functions and turns it into a regular dumb keyboard but it made no difference to the media keys.

(note: the below outputs are from pressing the keys in the same Stop, Previous, Play/Pause, and Forward sequence)

When I run sudo showkey -a and press each media key, the terminal cursor just blinks.

If I run sudo showkey -s, i get the following output-

0xe0 0x24 0xe0 0xa4 
0xe0 0x10 0xe0 0x90 
0xe0 0x22 0xe0 0xa2 
0xe0 0x19 0xe0 0x99

This is what the output of xev looks like

KeymapNotify event, serial 40, synthetic NO, window 0x0,
    keys:  4294967275 0   0   0   0   0   0   0   0   0   0   0   0   0   0   0   
           0   0   0   0   0   0   0   0   0   0   0   0   0   0   0   0   

FocusOut event, serial 40, synthetic NO, window 0x7c00001,
    mode NotifyGrab, detail NotifyAncestor

FocusIn event, serial 40, synthetic NO, window 0x7c00001,
    mode NotifyUngrab, detail NotifyAncestor

KeymapNotify event, serial 40, synthetic NO, window 0x0,
    keys:  2   0   0   0   0   0   0   0   0   0   0   0   0   0   0   0   
           0   0   0   0   0   0   0   0   0   0   0   0   0   0   0   0   

FocusOut event, serial 40, synthetic NO, window 0x7c00001,
    mode NotifyGrab, detail NotifyAncestor

FocusIn event, serial 40, synthetic NO, window 0x7c00001,
    mode NotifyUngrab, detail NotifyAncestor

KeymapNotify event, serial 40, synthetic NO, window 0x0,
    keys:  2   0   0   0   0   0   0   0   0   0   0   0   0   0   0   0   
           0   0   0   0   0   0   0   0   0   0   0   0   0   0   0   0   

FocusOut event, serial 40, synthetic NO, window 0x7c00001,
    mode NotifyGrab, detail NotifyAncestor

FocusIn event, serial 40, synthetic NO, window 0x7c00001,
    mode NotifyUngrab, detail NotifyAncestor

KeymapNotify event, serial 40, synthetic NO, window 0x0,
    keys:  2   0   0   0   0   0   0   0   0   0   0   0   0   0   0   0   
           0   0   0   0   0   0   0   0   0   0   0   0   0   0   0   0

For some reason, upon trying to set global shortcuts again, when input a custom shortcut, the media keys are now being detected correctly in the System Settings menu but they still don’t actually work, and I’m still getting the same output from xev and showkey.

I tried booting into my Windows install, and the keys work just fine.

The last thing I’ve tried was creating a test user profile. I rebooted and logged into the test profile and the media keys work. I logged out and logged into my actual user account and they’re still not working.

I would really like to avoid having to create migrate to a new profile, so could anyone please advise me on how to troubleshoot the issue further, or even (hopefully) how to fix it?