2004 Volvo XC70 rear Brakes lock up momentarily on back up

If you just bought it, did you get any type of warranty? Even if you bought it as is, if you just recently just purchased it at a dealership, you have some sort of guarantee that what you just bought should be in working order. Also what happenes if you keep going in reverse after it releases? Does the brakes grab again and release? Are there any warning lights on like the ABS or traction service light? To start with, you may want to call Volvo and see if they can scan all the control modules for you and see if there are any codes for brakes or the differential?

This is a responds to your responds to my question, no lights, no re grab, no warrenty, was in perfect working order when got it and the brakes system was checked per volvo's over a 100k inspection prior to purchase, this is a very reputable dealership I can trust and they will stand behind it even with out a warrenty. I was mearly trying to learn more about the problem before going to them. If you have more info to share with the info I just gave you that would be great.

SOMETIMES IF THE BRAKES ARE AFTERMARKET, THEY WILL GET STUCK OR MAKE ABNORMAL NOISES. EVEN NOT HAVING PROPER LUBRICATION IN THE CONTACT POINTS WILL CAUSE ABNORMALITIES.