Good for you Erik, you're fast xD sorry for answering so late.
In your Xorg.0.log doesn't appear 2 eGalax devices (tablet and pointer), this is because "usbquirks" isn't being applied. You correctly find what causes this problem, only grub2 uses /etc/default/grub or /etc/grub.d/* files ( https://wiki.ubuntu.com/Grub2#Grub%202%20Files%20&%20Folders ).
Remember, this is only a temporal fix, the bug still alive.
Good for you Erik, you're fast xD sorry for answering so late.
In your Xorg.0.log doesn't appear 2 eGalax devices (tablet and pointer), this is because "usbquirks" isn't being applied. You correctly find what causes this problem, only grub2 uses /etc/default/grub or /etc/grub.d/* files ( https:/ /wiki.ubuntu. com/Grub2# Grub%202% 20Files% 20&%20Folders ).
Remember, this is only a temporal fix, the bug still alive.