A meter set on continuity will quickly find a simple short. Set it on the 200 ohm resistance setting and check all pairs - are they all reading same values? Compare known 'clean' pairs to the troublesome ones. If you see rapidly cycling resistance values then the pair is probably being used for a phone line.
A tone generator would be the next thing to use if you are trying to identify which pairs you're using. That does mean you need access to the junction box/es in the system. If the resort is squeamish about granting access - and they probably should be - then you ask nicely to spend some time with their comm/data/phone technician or contractor. Put a tone on pair 1 and see if where it appears in timing shack or hill wiring. record results, move on to pair 2., rinse and repeat.
My guess is someone has changed phone line assignments and you have a landline on one of your timing pairs. Phone tech should be able to find a spare pair and move you over.
I've got my club wiring completely off mountain phone lines now, but the process was a lengthy one because of budget constraints. Back in the years when we were sharing cables and timing on unused pairs in their phone system, it was very important to diagnose problem but not make any changes without permission. Notes taken in exhausting detail and then present a clear request for changes to the maintenance manager. Generally I did the work myself after going over it with their people.
