I think this may be related to the issue.
$ xmodmap -pke | grep -i scroll ... omitted unnecessary hits. keycode 185 = XF86ScrollUp NoSymbol XF86ScrollUp keycode 186 = XF86ScrollDown NoSymbol XF86ScrollDown
I think this may be related to the issue.
$ xmodmap -pke | grep -i scroll
... omitted unnecessary hits.
keycode 185 = XF86ScrollUp NoSymbol XF86ScrollUp
keycode 186 = XF86ScrollDown NoSymbol XF86ScrollDown