Thanks for info - seems the voltage was just at the limit of the regulator's range. Changed back to original 1,5K resistors (from 1,8K) so now DC out is 19,5V (before 21,5V) from a AC18V transformer. All leds are on. Problem here is the mains moving from 210 to 230V and those swings seem to affect the whole GRLV system.