For $29/mo, we provide access to advanced level technicians who will answer your questions on any Macbook board related matter to the best of their knowledge promptly & walk you through how to solve your problem so you can deliver a working board to your customer.
Check DDRREG for corrosion or pry damage. Or shorted components. I fixed one with corroded resistors and caps on that line.
I've known someone who would reflow the RAM chips to fix possible broken balls.
Put the board in an oven at 250*F for 5 min... Then reflow the ram... If you don't have a good hot air station your screwed. Use lots of flux and a big nozzle.
To give the board an even heat.
Without preheating the board, a lot of the heat applied with the rework gun will be lost into the ground planes of the board resulting in "popcorning" the chips.
I second reflow RAM. The boards are long but not very wide, they are susceptible to flexing when abused. I have fixed several macbook airs with this issue from schools. Preheated board, used proper flux. They haven't come back.