The suggested workaround, running Activity Monitor and Quit - Force Quit'ing "coreaud..." worked for me. Apparently, the same can be done by running sudo killall coreaudiod in Terminal. I suppose restarting the mac would also accomplish the same.

No, you can have no caption tracks be a default. The expected behavior in that case is that a player will not have captions selected when first playing the video, with the exception of when the device accessibility setting CC + SDH is toggle On, in which case a track that matches languages with the device's language (e.g., for me, any of the "en" tracks) will be selected even if it isn't marked as the default one.