in early july the team made the choice to upgrade to unity 2018.2 because at first glance it appeared that it would have some solid performance benefits and no major inconsistencies from the previous version. It was a risk but one they felt was worth it for the benefits. they were right about the benefits but they were wrong about inconsistencies. It turned out their shaders became incompatible and needed to be redone. This caused a delay much longer than they anticipated.
Towards the end of july, as people were submitting bug fixes and uploading new art assets from their local builds to the shared build the magnitude of new art assets overwhelmed the atlases that they use. This has caused another unforeseen delay as they have had to find an alternative solution to be able to include all the new art in the game. They have found a solution and are doing that conversion. The bad news is the delay it caused but the good news is that all the new content that will be included in a17 is awesome and will be able to be supported.