Over the weekend I pushed out a small but important update to my starter master pages. When I originally created the starter master pages I used both the Design Manager feature as well as Seattle and Oslo to decide the best place to put things in the master page. There was a discrepancy between where the Design Manager and the default master pages placed the SPWebPartManager control. Turns out the Design Manager puts this control in the <head> section which is incorrect, it should be in the <body>. Having the control load before the <body> caused a host of mysterious problems so I have moved it to the body and I urge everyone to follow suit.
UPDATE: All of my starter master pages can now be found here: https://github.com/rdrisgill