This is very strange. I installed the repository extension on my site.

When I upload images as moderator/admin is works just fine.
When I login to a test account I have made and upload an image. It tells me that my image has to be approved by a moderator etc. Which is fine, but here's the thing.

I upload the image and finish the form, hit Upload. It redirects me back to page where the module is located and says, "A critical error has occurred. An unexpected error has occurred." When I go back into my Admin account the image is sitting in moderation que. I'm pulling my hair out trying to figure out what it is.

Using the latest version of DNN Community Version and 03.05.04 repository, although I've tried the beta version 03.05.06 and it gives me the same error. Would just like to make it go away as it is not effecting anything in the upload process. Just gives the error for no reason.

i got this issue on dnn 6.2 and it was an SMTP server issue, it can be configured from the host settings-> advance setting->SMTP Server Settings but i dont know if it may be the same direction for you.