Form3 platform error


9 hours printing, 1 hour to go, Grey V4. Printing stalls.
Front menu doesn’t show, but printer menu shows “platform error”.
All though platform is in position, print is not very heavy and nobody has touched the printer or table during the night.

I started out on support, but none to this problem. then switched off, lifted platform by turning spindle by hand.
But what caused platform error and how to avoid in the future?