This one’s not on HammUEr, but on UE itself as far as I can see.
Did you re-import the whole thing over an existing import?
Because if there are already previous versions of the assets, it can sometimes take UE a while to catch up and re-save the new one, especially if there are almost 2000 meshes (I’m assuming this is the same vmf file you sent me before).
From the error message, it looks like the older versions that needed to be deleted and replaced by the new ones by UE are still in the asset files, which causes it to crash.