I will ask the dumb question.
Was your parking brake on ?
Stuck calipers on a nearly new machine is pretty unlikely but anything is possible.

 

Did you mean if brake lights on ? Yes they are always on when rear brake is stuck. I wait two days. Brake lights returns to normal and caliper seems to release the disc a little bit. But when I press the pedal it is stuck again. Are there any special technique for bleeding rear brakes ?

 

Probably the slider pins are sticky and not releasing after you hit the brake lever.

 

Agree, sounds like the classic symptoms of a caliper sticking on the slide pins. And I also agree that it's odd to have that issue on such a new machine.

You'll need to remove the rear caliper to ascertain what the issue is and address it, paying close attention to the caliper slid pins, they should move freely allowing the caliper to fully release the brakes.

Another possibility, but even more unlikely on such a young machine is a caliper piston that is stuck or sticking. If the pins are lubricated and slide freely as they should, almost the only other possibility is a sticking caliper piston.

And the least likely of all is an actual hydraulic issue. A pinched, obstructed or otherwise compromised brake flex hose will function for brake application, but will not allow the brake to release quickly as it should. I've seen this countless times on automotive brake systems, usually caused by a flex line keeper that has corroded to the point that it is beginning the squeeze the flex line. In that case the hydraulic pressure generated by a normal application of the brake will overcome the pinched line, but allowing the fluid to retract is very slow and doesn't allow complete release causing the caliper to drag.

 

Hey did you get this issue resolved

 

Were you able to solve the problem? What was the problem? Was the fault fixed under warranty? I have exactly the same problem with a nearly brand-new machine. It's only a year old.