Just a tip. I upgraded to SCSM 2016 for customer and consequently upgraded Cireson Apps to 2016 versions. We shortly discovered that in general everything is fine, its not broken, people can get work done. But the Group Assign app crashed when using the Task button. Error was something like "System.NullReferenceException: Object reference not set to an instance of an object." and something more but forgot to take a screenshot.
My tip is that I unchecked the "Use Default Container Checkbox" (AD lookup) just to check if that changed anything. After that it stopped crashing. This setting is new compared to the last version they had. A weird thing is that when I rechecked this checkbox to really really confirm it's still ok. Does not crash.