RAM chip doesn't always work in Sony Vaio Laptop

I have a Sony Vaio GRZ660 notebook computer. It is out of warranty (more than 2 years old.) It has 2 slots for memory chips. Both chips work fine in 1 of the 2 slots. Recently, I have noticed that for the other slot, the memory chip will only work sometimes. It may have been doing this since I have owned it. I have cleaned the contacts on both the chip and in the socket as best I can. If I press on the socket to deform it slightly before I place the chip in the slot, the computer will boot up and show that this chip is working. However, the next day and days after, the memory isn't recognized. I think the socket slowly returns to its former dimensions, which is too big for the chip.

I think that the slot is slightly bigger than the thickness of the circuit board that makes up the memory chip, because the board feels a little loose after it is placed in the socket..

If this is the case, what is the best solution?

1. place a thin film of solder on each contact tab (there's about 20 on each side of the board and are close together).
2. some other solution?

Thanks in advance,

Mark