We handle all our threads seriously, however since there isn't anything else that we can do about this thread given that the issue was determined to be a server issue because the duplicator package worked fine when moved to another server.
So all procedures were followed and done. In terms of a recommended plugin i'm not aware of any other that does creation of Posts from the frontend.
The ones i mentioned previously were messaging plugins. To get this to work I would recommend just trying to temporarily switch to different server, but this particular issue won't be debugged any further.
Also as a part of our support policy we recommend opening a new ticket per query to help to keep things a organised so other customers can use threads like these to help with their queries.