I have a Lenovo T440s Model 20ARS0BH00 with 4GB Ram soldered and an 8GB Ram stick in the single slot of the mainboard. On some boot ups the laptop recognizes only the soldered 4GB and on other boot ups it recognizes the full 12GB. I have swapped the RAM stick in case it was damaged, but that did not help. Has anyone experienced this problem? I love this laptop, but a full mainboard swap would cost too much for a 5yo laptop.