Having to click twice to bring up SD

Minor but curious issue. Using firefox, my home page is a “newtab” page, with big thumbnails or tiles ( 16 total ) that are my most used bookmarks for easy access to them, of which the SDMB main forum index ( the SD home page? ).

When initially opening the firefox browser, I need only a single click on the SD time to launch SD. After navigating away from SD to other various sites and browsing ( on the same tab ) if I attempt to bring up SD again, I have to click twice to launch SD. Always, and it only affects the SDMBs.

If I close firefox and reopen it, SD needs only one click. Same if I just open another tab.

Admittedly, a first-world problem if ever there was one, but I am and always have been a curious sort. Any ideas?