[mythtv-users] subtitle matching rule not working

[Bill Williamson]

We have a new channel in AU called "Go!" which is showing reruns.  I
have a rule set up for Seinfeld as "any time any channel" and "match
duplicates using subtitle."

The show shows up in the list as:
Seinfeld: "The Watch"
and so on, so it has a subtitle.  Despite this it will NEVER match duplicates.

How can I debug this?  I've also tried "subtitle then description"
which made no changes.