Finally found touchpad fix for Lenovo Ideapad 5 15 (not 14 !) with synaptic touchpad

[KesLE6]

Maybe add this as tutorial, idk

So the Lenovo Ideapad 5 14 and 15 (LI515) have touchpad issues. This was a fix for the LI515. But this only worked with the widely used Elan touchpad. Mine for some reason was a synaptics touchpad, but similarly it would fail sometimes.
To fix this you can simply reload the i2c_hid module:

sudo modprobe -r i2c_hid && sudo modprobe i2c_hid

[pobrn]

Could please run sudo dmesg | egrep -i '(hid|i2c|syna|elan)' and post the output when it fails to work after reboot?

[KesLE6]

Well I would have to restart a lot to get that bug again. Luckly I saved a screenshot