My guess is that the problem is related to the webpage formatting. Without knowing the format of what you are copying, the problem could be a matter of "Paste Options" you have selected rather than a particular browser.

Are you pasting from the II webpage into a word processor? If so, here is how MS Word handles that...

When you copy content from a formatted source, such as a webpage or another Word document, you can select options at the time you paste it into your document.
1.Click or tap where you want to paste the content.
2.Press CTRL + V and then select Paste Options.
3.Hover over the buttons for a live review.

Additional info is at this link: https://support.office.com/en-us/article/Control-the-formatting-when-you-paste-text-20156A41-520E-48A6-8680-FB9CE15BF3D6

The combo of LastPass and Firefox has been more stable of late. It failed yesterday, when I noticed the black LastPass icon in the menu bar.

I now know what to do to quickly recover when this happens:
RightClick on LastPass icon > Remove Extension
Google LastPass > Download LastPass for Firefox
Log back in to LastPass
Icon turns Red on Menu Bar

You should not have to remove LastPass, download, and reinstall.
The black LastPass icon just means that you are not logged on to LastPass. This can happen depending on your LastPass settings, or if you have cleared your browser's cache.

Thank you.
OK, I'll try that next time.

Last year, when I kept getting the problem, I could not just log in. It would go into a loop and not log me in, so I went through the removal / reinstall process.