There seems to be a issue with the github 4.14 branch that causes things like static mesh generation to not work properly. Static meshes are regenerated every single time you load the project causing long loading times. Instead of only needing to be generated if there are changes.
You can tell by loading any UE 4 Project in the 4.14 waiting until it is fully loaded and built, and restarting it. Notice the long load time and output log of rebuilding meshes it has already built.
Compare this to the 4.13 branch which has little to no loading time as everything isn’t rebuilt.
This was most likely due to the commits made over the past few days changing the way versioning and static mesh generation works.