Unable to type $ symbol in Ubuntu

Question

I am unable to type the dollar sign ($) using Shift+4 combo in Ubuntu. Nothing happens when this combo is pressed.
The issue was first noticed in 16.04, and continues after upgrade to 17.04.
As this is a dual boot Ubuntu and is not frequently used for programming, this issue was noticed only recently. Hence I cannot remember if any new app caused this issue.

Some more details regarding the system and debugging:

• The laptop has a standard keyboard (no special currency symbols etc), with keyboard layout set as US in Ubuntu.
• Shift key, and 4 key works individually. Shift+3, Shift+5 combos work correctly.
• Shift+4 combo works correctly while booted to Windows, and $ sign appears correctly.
• Tried typing $ sign with on-screen keyboard in Ubuntu (on-board), but nothing happens when I click on Shift key and then the 4 key.
• Can type $ using unicode (Ctrl+Shift+U 0024) in Ubuntu

It would be really helpful if anyone can provide directions on how I can debug this issue or info on any known app causing this.

xev output for Shift+3:

KeyPress event, serial 28, synthetic NO, window 0x4000001,
    root 0x20a, subw 0x0, time 386927, (870,72), root:(870,124),
    state 0x10, keycode 50 (keysym 0xffe1, Shift_L), same_screen YES,
    XLookupString gives 0 bytes: 
    XmbLookupString gives 0 bytes: 
    XFilterEvent returns: False

KeyPress event, serial 28, synthetic NO, window 0x4000001,
    root 0x20a, subw 0x0, time 387092, (870,72), root:(870,124),
    state 0x11, keycode 12 (keysym 0x23, numbersign), same_screen YES,
    XLookupString gives 1 bytes: (23) "#"
    XmbLookupString gives 1 bytes: (23) "#"
    XFilterEvent returns: False

KeyRelease event, serial 28, synthetic NO, window 0x4000001,
    root 0x20a, subw 0x0, time 387208, (870,72), root:(870,124),
    state 0x11, keycode 50 (keysym 0xffe1, Shift_L), same_screen YES,
    XLookupString gives 0 bytes: 
    XFilterEvent returns: False

KeyRelease event, serial 28, synthetic NO, window 0x4000001,
    root 0x20a, subw 0x0, time 387224, (870,72), root:(870,124),
    state 0x10, keycode 12 (keysym 0x33, 3), same_screen YES,
    XLookupString gives 1 bytes: (33) "3"
    XFilterEvent returns: False  

xev output for Shift+4:

KeyPress event, serial 28, synthetic NO, window 0x4000001,
    root 0x20a, subw 0x0, time 607916, (648,613), root:(648,665),
    state 0x10, keycode 50 (keysym 0xffe1, Shift_L), same_screen YES,
    XLookupString gives 0 bytes: 
    XmbLookupString gives 0 bytes: 
    XFilterEvent returns: False

KeymapNotify event, serial 28, synthetic NO, window 0x0,
    keys:  10  0   0   0   0   0   4   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   

KeyRelease event, serial 28, synthetic NO, window 0x4000001,
    root 0x20a, subw 0x0, time 608219, (648,613), root:(648,665),
    state 0x11, keycode 50 (keysym 0xffe1, Shift_L), same_screen YES,
    XLookupString gives 0 bytes: 
    XFilterEvent returns: False