I'm having difficulty working with, and saving Export Rules in an earlier Build of 12.1 Web Viewer (158). Will I gain anything by updating?
12.1 Web Viewer work involving the Export Rules began in Builds 160 and 163. The major correction came in Build 167 with more following in Build 169. There was definitely work done in the area where you are having difficulty. Of course there was work done in other areas of the application and that is why the recommendation is that you update to the most current GA Build level.