My normal process for opening a new tab is to press Ctrl+t and start typing the URL I want, then press enter once auto-complete shows the correct URL. Sometimes I want to open a bunch of tabs at once, so while the first tab is loading I'll press Ctrl+t again and start typing in the next URL. If I wait until the page has started loading this works as expected, and the new tab opens with the cursor in an empty URL bar. However, if I press Ctrl+t immediately after pressing enter, the new tab's URL bar will contain the URL from the previous tab. I can't always reproduce this reliably, it only happens when I'm working really quickly and I usually don't notice until I see that the URL bar contains both the old and part of the new address. It may also be more common with websites I haven't visited recently, I usually encounter it when paying bills which happens about once a month.