Description of problem:  On an Asus S400C laptop, with Fedora 22 beta and Gnome 3.16, trackpad is not functionning properly, and gives an erratic feel, i.e.:

1) right-click is not recognized anymore ans is often assimilated as lef-click left (it seems that in order to have the same usual function as right-click, I have to leave a finger on the trackpad and permor one click with the other; 

2) natural scrolling is not working anymore (either in GNOME apps or Firefox)

I've tried to adjust mouse/trackpad settings in GNOME settings panel and to start a session with a fresh user directory (no previous GNOME settings),  without success. 

Everything was working perfectly well with this laptop under Fedora 21 and previous.

Here are some info on my trackpad:

I: Bus=0011 Vendor=0002 Product=000e Version=0000
N: Name="ETPS/2 Elantech Touchpad"
P: Phys=isa0060/serio4/input0
S: Sysfs=/devices/platform/i8042/serio4/input/input11
U: Uniq=
H: Handlers=mouse0 event4 
B: PROP=5
B: EV=b
B: KEY=e420 10000 0 0 0 0
B: ABS=661800011000003