The left navigation in the build data pages always has one of its links active: the one that corresponds to the page you are in. The mechanism that applies the correct class to the active link is not working for the "build summary" page when you navigate directly to its errors section toastergui/build/<build_number>#errors or to its warnings section toastergui/build/<build_number>#warnings
Patch submitted to the mailing list https://lists.yoctoproject.org/pipermail/toaster/2016-September/005167.html
Sent to bitbake-devel and pushed into toaster-next.
fixed at http://git.openembedded.org/bitbake/commit/?id=f236d9ca28e45a270f50bb3edcd466b1bc8d2960