Description:
Sometimes the touch pad "tab" function stops working. See "steps to reproduce" for more details. The problem was introduced recently (before the system worked totally fine for over 6 months)


Additional info:
* libinput 1.2.2-1
* xf86-input-libinput 0.17.0-1
* system is a Lenovo Carbon X1, 2015 edition (3rd gen)
* kernel is 4.4.5.201603142220-1-grsec


Kernel synaptics boot log:
psmouse serio1: synaptics: queried max coordinates: x [..5676], y [..4758]
psmouse serio1: synaptics: queried min coordinates: x [1266..], y [1096..]
psmouse serio1: synaptics: Touchpad model: 1, fw: 8.1, id: 0x1e2b1, caps: 0xf003a3/0x943300/0x12e800/0x10000, board id: 3072, fw id: 1795685
psmouse serio1: synaptics: serio: Synaptics pass-through port at isa0060/serio1/input0



Steps to reproduce:
Work with the touchpad (tab and scroll around), after a while, the tab feature isn't working anymore, but scrolling and mouse movement seems to behave as expected. The logs show the following information
/usr/lib/gdm/gdm-x-session[XXXX]: (EE) libinput bug: unexpected scroll event 0 in area state

The tab feature can be restored using one of the following work-arounds:
* go to the GNOME system settings and disable and re-enable the tab settings
* try to "scroll" using 3 fingers, after some tries the libinput seems to behave normally again


Honestly I'm not sure if I'm tagging the right package here, so feel free to reassign the bug if required. Please tell me if I should report an upstream bug.