Originally Posted by nikoday
yes, I should be in diags mode, but I can't see any text due to display problem
Diags can crash like that (twisted boy under tree) if the diags kernel does not match the diags partition, or if the battery was too low to finish booting to diags.
While in diags mode, there is no screensaver or sleep mode, so the battery can discharge completely (making it appear bricked). It would be good to leave it connected to a charger (or host PC) while in diags mode.
P.S. The "twisted boy under tree" screen happens because the startup code assumes 608x800, but in diags the screen is actually 600x800. This is normal for a K4, but should only last a second or two before the diags menu appears (unless battery is too discharged).