You are writing about the years during the transition to lead (Pb) free solder. If you wanted to touch up the solder work it's a trivial job for any good technician.
Be sure to see how the move to lead free solder has caused an avalanche of failed electronics world wide.
I bought a Sony STR-DE845 tuner/amp about 7 years ago. After about 2 years of use it began to have issues. I would occasionally turn the bass to max, drop a speaker, etc. The the on/off switch quit working forcing the use of the remote to turn it on and off. Then I noticed that if you selected the A speakers or the B speakers you always got both on any setting. It continued to get worse until I replaced it last week. Based on my background I thought I would try to do a failure analysis.
Sony uses a stacked circuit board approach where connector pins on the 'motherboard' (they label it as the DISPLAY board) insert into sockets on other boards which are mounted above the motherboard. Since most of the problems seemed to be associated with the power switch and speaker select switch I pulled that board and found nothing apparently wrong with it.
However, when I examined the mating connector on the mother board, under magnification, it became apparent that the solder joints on 4 of the 5 pins had failed. (yes, I have photographs) The type of failure where solder on the pin has separated from the solder on the circuit board is frequently associated with mechanical shock/vibration or thermal cycling.
This type of failure, where the solder joint fails, usually leads to intermittent problems which is exactly what I was experiencing.
After photographing the failure at these pins I checked the other similar connector for the "MUTING" circuit board. Again 3 or the 5 pins had solder connection failures.
Mechanical causes of the failures can probably be ruled out since the unit has been sitting in the same place since it was wired into my system. Thermal expansion/contraction 'might' be the cause due to the large operating swing from room temperature to 'very hot' after operating for a couple of hours.
This type of failure should have been discovered during environmental testing at Sony, if they have such a program. The solution would have been to select a connector which provided more physical support for the connector pins on the motherboard. The connector sockets on the 'daughter boards' had good physical support and did not show any failures.
Looking back I have owned several Sony products and don't recall any of them lasting more than 5 years. I have tended to ignore this because when one failed I was anxious to replace it with a newer, more high tech, feature rich unit. Maybe Sony depends on that attitude.