So, i think I found a solution that works:
(First make sure the pen works by repairing bluetooth.)
Go to device manager -> Human interface devices : and find USB Input device. (Its the last entry for me)
Go to the devices Energy settings (if the tab doesn't exist it's the wrong device) and disable the first check box so the pen is never put to standby.
After doing this the pen works for me even after hibernation.
Solution doesn't work consistently.
regards
Acrosicious