Q:

Mouse scroll up not working in some applications

Scroll up is not working in some applications such as Firefox, Zotero, and when I'm browsing "open folder/file" section in Atom/VS Code. In other environments (Konsole, Dolphine, Chromium-based browsers, etc.), it works flawlessly. Any idea how to fix this?
This issue has been around since when I upgraded 18.04 LTS to 19.04.

My current setup:

OS: Ubuntu 20.04.1 LTS x86_64
Mouse: Logitech Gaming Mouse G600 (The same issue occurs when I'm using other mice so I assume this mouse is not the problem.

Here's what I found so far:

xev

"ButtonRelease event" and "ButtonPress event" do not show up when I scroll up.
Differences in mode (NotifyGrab vs. NotifyUngrab) and detail (NotifyVirtual vs. NotifyInferior)

scroll up
LeaveNotify event, serial 40, synthetic NO, window 0xd800001,
    root 0x6c9, subw 0xd800002, time 11818211, (27,58), root:(2935,585),
    mode NotifyGrab, detail NotifyVirtual, same_screen YES,
    focus YES, state 18432

EnterNotify event, serial 40, synthetic NO, window 0xd800001,
    root 0x6c9, subw 0xd800002, time 11818211, (27,58), root:(2935,585),
    mode NotifyUngrab, detail NotifyVirtual, same_screen YES,
    focus YES, state 16384

scroll down
ButtonRelease event, serial 40, synthetic NO, window 0xd800001,
    root 0x6c9, subw 0xd800002, time 11885441, (42,35), root:(4344,59),
    state 0x1000, button 5, same_screen YES

LeaveNotify event, serial 40, synthetic NO, window 0xd800001,
    root 0x6c9, subw 0x0, time 11885441, (42,35), root:(4344,59),
    mode NotifyUngrab, detail NotifyInferior, same_screen YES,
    focus YES, state 0

ButtonPress event, serial 40, synthetic NO, window 0xd800001,
    root 0x6c9, subw 0xd800002, time 11885529, (42,35), root:(4344,59),
    state 0x0, button 5, same_screen YES

EnterNotify event, serial 40, synthetic NO, window 0xd800001,
    root 0x6c9, subw 0x0, time 11885529, (42,35), root:(4344,59),
    mode NotifyGrab, detail NotifyInferior, same_screen YES,
    focus YES, state 4096

xinput

You can see that button4 (i.e., scroll up) is not turned off.

$ xinput get-button-map 10
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20

A:

It turned out that this was due to the following lines in ~/.xbindkeysrc.
"xte 'keydown Control_L' 'key t' 'keyup Control_L'"
b:4

The problem is solved after commenting these out.

