edit2: I could confirm this problem happens on amazon.co.uk when ublock origin is enabled. It is uBlock origins fault, so the only solution is either disable Ublock origin on this website or disable my adblock for amazon prime in the advanced settings, but u wont see subtitles since that is ublocks issue.

have not been notified, interesting bug
edit: i am not sure if i can replicate the bug. if you continue to have the problem maybe you can join the discord https://discord.gg/5fBYathA7d or go onto github. Skipping forward and back 10s should temporarily reset the subtitles.