What render engine do you use ? From our tests, the RAM and CPU usage seems normal, we dont get that 100% spike. Please, try to reproduce the problem in a stripped scene and send it to us.
About the faulty scene, there are not significative differences between Forest Lite and Pro loading the files. Usually these problems are caused by missing textures or references, although 40 min. is too much. As before, please send us the scene and will check it.