Sometimes, in our QB 5.1.16, after build failure, there is no possibility to open the failed step log (by clicking on a "sheet of paper" on the side of the step).
Even though the new window in browser opens, it is almost empty, showing only the top bar with step name and "show steps" checkbox. Also, when clicked the "save" button in that window, the browser downloads an empty file "full-log.txt" (0B of size).
Is it some issue with QB itself or with building machines? It's hard to give more specific information about that, because we cannot guess where could be the problem and why is that happening. That issue reoccurrs randomly, in many various configurations and on various machines.