I watch Amazon Prime video on my on my TCL 65s425-CA with built in Roku 7133X, software 9.2.0.4502 and the sub titles are all over the map. I’ve selected English, and no captions on both the Amazon settings and the Roku settings. I get everything from different languages to descriptive style subtitles that note background noises.
Prime Video is really the only problem for the TCL/Roku combo.