Heres a puzzle.

Recently had some building work done.
We have a 2 way light in the kitchen.
One of the switches was replaced as part of the building work.
However there seems to be an issue. Its not switching correctly.
(As far as I know it used to work ok although Im not 100% so it
may have already been broken).

Both switches have 3 core wire behind them. With the switches
removed there seems to be no continuity between the com core
of the cable.

Is it possible to have a 2 way switch wired at one end without
using 3 cores on maybe one side.

(The cable is joined into a ceiling junction box which is very
difficult
to get access to. I suppose getting at that would answer my question
but just before I do can anyone help.)

Matthew