UMS5: print does not start! :(

[aag 6]

My UM S5 has an issue that I do not understand. When I start the print, it brings up the plate, it does the active levelling ... and then the printhead goes to the left back corner, both LEDs on the printhead stay red, and the display says "Ready to print". And nothing happens. Then I reluctantly cycle the power (I haven't found a way to do a "warm reboot"), and randomly, on the 2nd or on the 5h attempt, the UM starts printing. This is very frustrating. What might possibly be going on?

Edited February 8, 2019 by aag

[Schoffra 1]

did you have any solution to this? I have a similar issue

[Dustin 150]

Unfortunately, UltiMaker does not provide direct support via the Community.

Please contact UltiMaker Support directly for help with this issue.

here: https://support.ultimaker.com/s/contactsupport