The SwaggerUI was working perfectly fine but then later stopped working completely.
I checked the logs and found the error to be this:
The service interface name "["Magento\\Store\\Api\\StoreRepositoryInterface","Magento","Store","StoreRepository","Interface"]" is invalid.
I have already tried restarting the server and disabled caching as well but still no luck.
Which version of Magento are you using?
Did this happend after an upgrade or module installation?