Comment # 7 on bug 1158190 from Michael Lanczak

I remember me, after upgrading of Leap 42.3 to version 15.1 all runs perfect.
Then I had done a system safe of the root partition (sda2) from this upgrade,
but not safed the boot partition (sda1). After some time I installed Leap 15.1.
new complete. Then I got this described problems with keyboard and mouse inputs
laming and delaying. 
Now I recovered my upgraded (Leap 42.3 to 15.1) system safing (sda2), start the
system new and all blocks in the boot sector by started GRUB, starting was not
possible! So I came to the result, that in Leap 15.1. anything was changed in
the bootsector in GRUB. 
I recommend, first try installing the previous boot sector GRUB from Leap 42.3
.