@User another test is on mouse buttons: run xev -event button , go with the pointer to the center of the white xev window, press and release left button... do coordinates have a reasonable value? (156,131 in my case, and seems reasonable, these are offsets from the upper-left coordinate of the xev window)

ButtonPress event, serial 25, synthetic NO, window 0x2400001,
    root 0x6a9, subw 0x0, time 1274949, (156,131), root:(195,220),
    state 0x0, button 1, same_screen YES

ButtonRelease event, serial 25, synthetic NO, window 0x2400001,
    root 0x6a9, subw 0x0, time 1275070, (156,131), root:(195,220),
    state 0x100, button 1, same_screen YES

Sorry for the delay in replying. I tried clicking and releasing once, and then I moved the window and clicked and released again.

chrisj@debvm:~$ xev -event button
Outer window is 0x3c00001, inner window is 0x3c00002

ButtonPress event, serial 25, synthetic NO, window 0x3c00001,
    root 0x3ac, subw 0x0, time 12753835, (81,100), root:(81,793),
    state 0x0, button 1, same_screen YES

ButtonRelease event, serial 25, synthetic NO, window 0x3c00001,
    root 0x3ac, subw 0x0, time 12754652, (81,100), root:(81,793),
    state 0x100, button 1, same_screen YES

ButtonPress event, serial 25, synthetic NO, window 0x3c00001,
    root 0x3ac, subw 0x0, time 12761296, (78,95), root:(122,213),
    state 0x0, button 1, same_screen YES

ButtonRelease event, serial 25, synthetic NO, window 0x3c00001,
    root 0x3ac, subw 0x0, time 12762103, (78,95), root:(122,213),
    state 0x100, button 1, same_screen YES

The first set of coordinates seem like they are relative to the origin of the window, the second set seem to be relative to the corner of the VM screen (root window?). I think that looks like what you were seeing. If I click and release quickly then the release event doesn't get logged.