Hello, i published 4 days ago the post that @Raphael has mentioned above.
It’s really very simple the problem and the solution, so i recommend to you that read it.
Basically the NGINX default settings BLOCK the access to “hidden” files/directories (those starting with a period), and Nextcloud manage the uploading of big files (files bigger than 9.3Mb!!!) splitting the upload in several chunks of 10000000 bytes, which are re-assembled once uploaded the “last bit” in a file with filename just “.file” (with a period as first character !!!). It probably is a bad decision from the developers of such “chunk” system… i don’t know.
But briefly, the solution consists in add an exception rule in NGINX configuration file to not block the “.file” access… and voilà, your Nextcloud run perfect! then the “.file” file can be moved to their destination user directory without any problem.
In my post i give you the details step by step: it’s recommendable to create a new NGINX template config file, and then assign it as “Proxy template” to the host where you have running Nextcloud. In this way this change will be permanent although you update HestiaCP or its servers (açpache, nginx, etc…) in the future.
Please, comment here if you get it work fine also with Owncloud 
Cheers!