jeffreydesign wrote:
Sounds like a loose connection - but where? The first place I would
check is the circuit breaker....
Somewhere between the circuit breaker box and your fixture there is a
loose connection and I would consider it VERY unsafe and a potential
fire hazard. ...

Given that the symptom appears to occur only in one fixture, it would
appear localized well beyond the circuit breaker...as I noted in
another response, I would venture most likely is the fixture base
itself, then the connection _to_ the fixture, then internal in the
fixture...after eliminating those possibilities I'd start casting a
wider net...

I don't disagree it is a potential hazard...

... Find a different electrician. No self-respecting
electrician would EVER leave a homeowner with the described condition,
furthermore if that electrician wants to keep working and avoid having
the liability of a fire (and all the consequences that can accompiany
that) on his record.
.....

Well, they say they've tried three already...agree it would seem they
should have been able to isolate something, but this is a little
over-the-top on liability -- if they didn't do anything, there's little
they can be liable for imo. Inability to find/solve a problem not of
their creating isn't an offense that I'm aware of...