I noticed same problem after last update - browser switch to the nearest tab automatically, but not to last active tab. And i was never use any extentions, switching tabs was at normal usual order for me. Classic tabs extention option "When closing a tab" has no effect at all - no matter which option is turned on. But I made such a thing and it helps a little - install "Classic Tabs", go to its settings, activate "Open all tabs next to the active tab" with "and place consecutive new tabs in order". Now it works almost like it was - new tab opens just next to active, even if it's in the middle of all tabs, and switches to previous active tab when closed. So, i think you should try the same way.