I ran into some odd behavior today and wanted to report it as potentially needing a fix.
I created a new library and made sure I had it selected as my working library. I then added a second condition to an existing rule. When I clicked the "Save to Library and Build" button the build failed. The reason given was that revision x was already in the upstream. I checked the upstream and sure enough, the upstream contained revision x and my attempted build contained revision x (latest). I then looked at the rule and selected "Compare Revisions" in the left pane it showed revision x without my change, and in the right pane it showed latest with my change. At a loss I deleted the new condition from the rule, then recreated it and the build succeeded.
I needed to add the same condition to a second rule, and again ran into the same issue. This time I deleted the new condition and successfully rebuilt the library. I then added the condition a second time and the build succeeded.