Hi guys,
Thanks for the responses.
In brief response to your questions:
The extension A appears as a DSS/Busy Lamp key on extension B.
Extension B is in a ring group with extension C but not extension A (extension A forwards to the ring group containing B + C).
Extension A does not forward to a button appearing on B.
We are not using UCA.
After Ralph's query regarding the keys I decided to remove the DSS/Busy Lamp key as a test. This corrected the issue and extension B was no longer able to bypass extension A's call forwarding. I then re-inserted the DSS/Busy Lamp key expecting it to cause the unwanted behaviour again; however this has not happened and extension B is still unable bypass the call forwarding on extension A.
So it would seem, problem solved. My only question is, is this known bug (hence the queries around key assignments)?
Regardless, thanks for the help - much appreciated!