Thank you for reporting the issue. Unfortunately, I wasn't able to reproduce it. I tested the extension on multiple devices, including both Windows and Android, and "Select Subtitle" worked normally for me.

There also hadn't been a recent update when the issue was first reported. I checked the previous version as well, and the code responsible for this functionality was the same in both versions.

I've now released a new version that displays error information when the problem occurs. This should help me identify what is going wrong if the issue happens again.

As a first step, please make sure Firefox and the extension are up to date. If the issue still occurs, could you let me know whether it happens on every video or only on a specific website/video? Please also include the platform you're using (Windows, Android, etc.) and, if possible, the error information shown by the extension.