In fact, if you’ve installed the extension via this link Language Reactor sacrosanctx – Get this Extension for 🦊 Firefox (en-US), it’s not our extension; someone has probably modified our code and hasn’t updated it for a while. We should ask the Firefox Store to remove this extension so as not to mislead users.
That is why we cannot fix this bug in Firefox.
The official LR extension is only available on the Chrome Web Store via this link https://chromewebstore.google.com/detail/language-reactor/hoombieeljmmljlkjmnheibnpciblicm