Recently we added a functionality that allows import of 4D NIfTI as MultiVolumes. It has not been thoroughly tested, so it would be great if you could try it out and see if it helps.
To use it, you will need to place your 4D NIfTI file into a separate directory, and use MultiVolumeImporter module. Since your NIfTI file will not contain the metadata needed for the analysis (such as timing information), you will need to use MultiVolumeImporter to initialize those.
If the import is working for you from the GUI, you could then look into this function to automate the load process.
@pieper added this functionality to MultiVolumeImporter, so I cc him here so that he can follow the conversation.
p.s. In the future, if you want to bring my attention to your post, you should mention me with @fedorov - this way I will receive notification about your message. I do not regularly check all posts on the forum, so just mentioning my name does not mean I will read your message!