brake pedal pushes back

[jkern]

Had a panic stop about 3-4 weeks ago and then some front end damage to my 2011 listed below. all the damage seemed to be body related with the bumper and front clip involved. Got the truck back the other day and now the brake pedal occasionally pushes back to me when i lightly touch the pedal. it seems to only do it when i have not used the brakes for a long time or after i first start the truck. My old 2nd gen did the same thing most of the time. the braking power/control doesn't seem to be affected. The power steering pump lines were removed for the repair, and needed to be bled during the repair, could the booster have a plug of air in it? any ideas??