The article's author mentioned that the problem is not limited to Samsung TVs - someone reported the issue on their phone.

The article does not mention a root cause, but I have a theory that it's likely a malformed subtitle track. I tend to watch with subtitles on so I run into related issues every once in a while. Most of the time it's one of two things:

• The subtitles are misaligned (eg wrong offset, addressed by adding a positive or negative delay to the track)
• Bad formatting on the timing information.

The latter can have multiple effects depending on what format the subs are in, but most of the time it's a missing end time, meaning that the subtitle stays on. However, some formats also have cues as to who the speaker is, and that comes with a start and end tag like in HTML. I suspect that in this case the end tag is either missing or misaligned in the syntax tree, causing this one line of dialogue to be displayed over and over when the player reaches other lines matching the cue for it, but that don't get shown because the user has turned subtitles off.

As to why this is bleeding into other shows: I suspect it's an issue with how the software clients are caching the subtitle files. This would also explain why going back into the episode that caused this fixes things, because it would reset the cached file. Which in turn brings me back to pointing the finger at Amazon, not Samsung, because Samsung would just be loading Amazon's software client to play the video and subtitles.