From shiki-tm:

about this issue i talked to you about affecting the last characters in a subtitle line. while i think yomitan has a problem with how itll render the popup size sometimes seeing this on my laptop was a little surprising. maybe there really is something strange with how the last characters are shown through asbplayer? did you ever look into this btw? sorry to suspect your extension but idk why ONLY the last 2 or 3 characters in a subtitle line are affected by this. if you ever have time to look into this id really appreciate it man. keep the amazing updates !

https://github.com/user-attachments/assets/754d6b34-44b5-4032-928d-383a5514c753

Speculative workaround: Reduce width of asbplayer overlay iframe