Can't import .obj with a lot of groups

We have an issue regarding loading .obj models from Houdini. We have a lot of buildings in the “city” and we are trying to import them. If we keep all of them as one group it loads fine, but if we want to import them as separate groups Unity just uses up all available ram and there is no log or message that we could find that would help as pinpoint the problem. Is there any way to override default obj importer or to at least have a log that will let us figure out what is the problem?

Please, check if it could help you ^^

Runtime OBJ Importer