Robert Baer wrote:

Definitely, mechanical stress seems to enhance or aggrivate the
migration of the solder.
Monitors exhibit similar problems; one or more colors get intermittent
and / or go out.
One then must re-solder the CRT socket to the PCB.
The mechanical stress comes from the sponge in the back of the case
that presses on the metal cage around that PCB.
I have fixed dozens of monitors that way, some 2 or three times.
The one i have was bought 12-15 years ago and fixed 3 times so far.
I have called it electomigration, because of the metal flow patterns
with regard to presumed current flow in each trace.

The problem is much simpler than that. The holes in the board are
too big, and as a result, the solder is required to bridge a large
gap. Solder has next to no ability to withstand repeated flexing, so
the relatively thin solder bridge flexes and cracks.

The answer is simple all joints should be good mechanical joints. The
socket will last longer if you bend its pins outward so that they are leaning
against the pad before you apply solder.

-Chuck