see also https://thunderbird.topicbox.com/groups/addons/Tadf090396736829b/browseraction-popup-html-not-reloaded-upon-second-button-click

clicking the browseraction button displays popup.html on first click only.

Consecutive clicking the browseraction button does not reload the html. It uses what is already copied into the DOM.

So if some action in the popup hides the html or sets it to "", it stays hidden when the button is clicked next time. Then, only an empty popup frame is shown. So changes persist.

In FF, the popup.html is reloaded everytime. So changes do not persist.

As standard8 writes in the forum post, both ways to handle could make sense.

It should be decided whether to follow FF or not, and put whatever is decided into the documentation, so that we know how to handle the popup content.

yes, I wanted to close it yesterday, works since the new 75 beta. Sorry for being slow.