I have noticed this happening. I don't know what's causing it - I actually haven't been able to reproduce it (the button works correctly for me on Android, Windows, Linux, and Mac).

It definitely should be behaving the same as any copy-paste operation since it is literally issuing select-all and copy commands.

My best guess is that it's getting copied as rich text, and pasting that rich text into certain types of text fields mangles it.
If it's possible, a potential workaround would be to force the copy to be plain-text only.

One way to do this is probably:
* Add a hidden text area
* Assign its contents to the page's innerText
* Copy the text area

So far I can only find two instances (from the same user) of this problem. It should still be fixed, but for now I'm going to lower the priority.

Sounds fine. I also wonder whether this might be related to locale.

P3 because I don't think we have continued seeing issues with this.

Thanks for checking. Let's close it in that case.