For years, this add-on has suffered from a persistent bug: after an unknown background action, the "Open" button in the Saved Sessions Manager suddenly stops working. I’ve spent several hours troubleshooting, but the technical root cause remains elusive.

Here is what I have established so far:

Profile Corruption: Something is corrupting the user profile. Creating a fresh profile resolves the issue, but only temporarily.

No Add-on Conflicts: I have 100% ruled out conflicts with other extensions.

Clean Install: The issue is not caused by leftover data; a full, clean re-installation of Firefox did not fix it.

The most important point: While I cannot pinpoint the exact trigger in the code, I am able to reproduce the bug reliably. I am happy to assist with further questions or testing.