Comment # 3 on bug 984955 from Michael from Offenbach Germany

Not sure if this is related:

But as I have the strong feeling that this issue has to do with USB handling,
there's another USB difference between the "last good known" 4.1.13-5.1 and
later kernels: 

When booting 4.1.13-5.1, pretty often, 1 out of 3 or sometimes 1 out of 2
times, it takes 30-120 seconds, before the plasma login screen / login manager
"detects" my usb keyboard and usb mouse AGAIN. When booting into the initial
GRUB2's boot options, keyboard and mouse are detected at once, and when login
manager is shown, no mouse moves or pressing any keys is possible. Even e.g no
"NUM LOCK" pressing, LED stays dark. After 30-120 seconds, without further
notice, everything starts to work fine. 

This was introduced some kernels before 4.1.13-5.1, I don't know, thought my
BIOS might be buggy first. And this behavior completely disappears with one of
the following "crashing" kernels. Never happens with them.