From the image you can see i have 2 assets one named Tree_Roots.FBX and one tree_Roots.tga when trying to import both of these at the same time it causes the error window to open seen on the right hand side, but if i reimport these assets once they are individually imported it wont crash, is this a known issue with build 1627304?
With UE4, all assets are imported into the engine as .uasset files. For this reason, all files in any single folder will need individual file names. You should notice when you import individually that you are actually overriding the first asset. You are able to bypass this if you import your files into separate folders, for instance into a Mesh folder and a Material folder.
Regardless, the crash is not supposed to occur and I have reproduced and logged the issue. Thank you for the information.