Screen refresh problem

Mid 2012 MBP Retina with 10.10.3 is experiencing intermittent issues with the screen not refreshing properly. This is happening in the window headers for Safari, Mail and Pages so far. The problem started after a logic board replacement and clean install of OS and all software with data moved manually back. This has happened 3-4 times now and Apple has no clue what is going on. Not happy because AppleCare expires in about 6 weeks.