I have experienced a similar performance problem with (at least) the last two WIP releases. Several weeks ago, I created a 2D view of a customer product using the make-2D drawing command. The result was a curve set consisting of 12193 elements. At the time I was able to transform the set without any noticeable delay. Today, using last week's WIP, I attempted to move the set to a new location and it took five minutes (plus or minus one second) to perform the transformation.
I analyzed the set and all the curves were reported to be valid.
I exported the curves to a Rhino 5 format file and, using Rhino 5, was able to perform the same transformation in one or two seconds. To cover my bases, I opened the new rhino 5 file in the latest WIP (5/16/2017) and made the same transformation. Once again the WIP required five minutes to perform the operation.
I am not making any claims regarding the quality of the curves, I am merely calling attention to the difference in performance between Rhino 5 and the current WIP when performing a basic transformation of the same set of data.