T23 memory slots problem

[madrigal]

Hi guys!
I have IBM T23 mobo with strange problem:
Both two RAM slots fitted with memory banks (tested, working OK) . When powering on it beeps well known sequence 1-3-3-1 (no memory in the slots). If I apply some pressure over the banks, laptop boots normally till the moment I release my fingers. At that point the system freezes (sometime at once, sometime after a while). It is obvious that there is some problem with the memory slots (loose contacts or something other). There is no problem with soldering (like well-known T30's problem) - I thoroughly observed them using stereomicroscope (after that I resoldered all visible pins just to be sure) - there is no change.
My question is: does it connected to the loosened contacts in the slots or is due to something happened to the inner rows of pins which are not visible like these on T30. In either ways if there is need for replacing the RAM slots (I have a dead T23 mobo) - how this could be done - if someone already had been dismantled T20, 21, 22, 23 RAM slots, please let me know the right sequence. I have relatively good equipment and think I could do the work - just do not want to break something without need.

Thank you in advance.