I have set firefox to open new tabs in the right side (at the end) using about:config setting
browser.tabs.insertRelatedAfterCurrent = TRUE

Foxy Gestures worked correctly as far back as I can remember.

But today Foxy Gestures started opening the tab directly next to the current one. It seems to ignore the setting browser.tabs.insertRelatedAfterCurrent

CTRL+T or the new tab button still opens the tab as expected.