Problems with 16x2 LCD - writes fine but after 10s disintegrates to weird chars

Tried to duplicate your experience with an arduino Nano and a parallel (12,11,5,4,3,2) 16x2 LCD display with A0 connected to pin 3 (contrast) of the display.
This the result: steady image "Dette er skrevet i loop. Exp". No desintegration whatsoever!