Dont stop the upgrade after the first break, reload the page with F5 (on windows systems) or alternate keys on other systems
if needed, reload the page (upgrade-script.php) multiple times, so that you see the buttons " Kick me to the Backend" in the bottom of the page at the end. "Worst case" for me was 8 reloads, but this was not a WB 2.10.x as start version
maybe you check the files or upload it again in Folder "install" and the file upgrade-script.php in wb-root.
it's important, that you have there the files from your target version (WB 2.12) - i see it again and again, that the guy's try it with the upgrade-script from the old version