Hey everyone, after having this problem, i found out the problem might not be the soldering at all. read on...
I have a MBP 15" early 2011, had the logic board replaced in the apple program for the video chip, after that, i started to get kernel errors once in a while, all was pointing to RAM, but could never actually find a defective stick and tried many, after a while of seating and reseating the sticks and a fresh install os the macOs it stopped for almost a year with no problems i thought i was done; only to begin crashing, powering off and beeping this week.
i've been reading forums about this problem and after watching this video
I'm having exactly the same problem as this.
So I took it apart again, and what did i find... apparently, as i said, and for everyones happines it migh not be the soldering at all!!
It seem the CLIPS that hold the stick closest to the keyboard are worn and do not have enough pressure so they do not hold the ram in place all the time, a little bump and the RAM stick springs up like half a milimeter and the problem appears.
What did i do? Got a 1.5mm (.60 cal) piece of flat styrene about 3mm wide and 7 or 8 mm tall, put BOTH RAM sticks in place and with a little plastic tip/spudger push down the stick closest to the keyboard so the clip can make its full travel inward and insert the styrene pieces one in each side in the slots between the clip and where the screws for the bracket are and then push them towards the RAM contacts to make pressure inward so the clips are pressed firmly against the sticks (you wont be able to remove the sticks without removing this styrene pieces).
I did this, the MBP started with no problems, i can now shake it and won't freeze and/or beep at all.
I'll try to make a video or at least a photo guide showing what i mean and post the link (it will be my first YT video so be nice hahaha) so it shows the fault and fix clearly.