In article ,
J.B. Wood wrote:

So, except for access to the laundry room terminal block and the
terminals in my unit there's really nothing else I can check either on
the outside of the building or elsewhere (which should be Verizon's
responsibility).

"Laundry room" rings a bell with me.

In a house we rented some decades ago, we had problems with line noise
on the phone, ring failures (the caller would hear a ring tone and
then an immediate disconnect) and other problems.

The problem turned out to be laundry-related, in a way. The line came
into the house in the kitchen, and was wired to one of the square
four-terminal line blocks before running up the wall to the phone.
This was located right next to the clothes washer.

It turned out that over the years, dirt and spiderwebs (and maybe some
soap dust) had gotten into the connection block, and build up on the
surfaces. When humidity was high (e.g. when we were doing laundry
with hot water) and the surfaces were cold (e.g. winter) moist air
would cause condensation inside the connection block, dampening the
surface contamination and creating a current leakage path.

It was bad enough that when the phone would try to ring for an
incoming call, enough current would flow to momentarily trigger the
central office's "off hook" detector, and the call would be
"answered"... and then drop out immediately.

The cure was straightforward: pop off the connection-block cover,
dust it out, scrub everything with a soft brush and some denatured
alcohol to remove the contaminants, dry thoroughly, close back up.
Problem gone.

I once had a similar problem, in which house moisture condensing
inside a Macintosh keyboard in a cold room would bridge the ADB "power
button" signal lines enough to cause the Mac to power itself on.
Cleaning and drying the PC board in that area, and then dabbing on a
thin layer of fingernail polish as a "conformal coating" fixed the
problem.

So, it might be worth checking your inside wiring and phones for any
places where cross-wire current leakage might occur. Clean, dry, and
if possible insulate against further contamination and moisture.