Maybe this is the change that is mentioned in the release notes of PMS 1.15.4.919?
(Subtitles) Auto select forced subtitles when not listening to foreign audio (#6126)
If that’s it, please don’t change it back again. Rather, add a new option if both ways should be supported.
I say that because I think this might fix my request from this thread: Unable to configure automatic selection of both forced and foreign subtitles (I’m not sure because I can’t test it yet because of the bug described here: [BUG - PMS 1.15 regression] Automatic subtitle selection broken)