What could be the problem when transferring files over SFTP?

Question

Network administration

Good time.
I connect to a folder on a vps that is running Ubuntu server 16.04. The user has a separate group, the folder is available only to this group. I use the folder as network storage. From windows I connect using the SFTP Net Drive 2017 program . I mount as a logical disk. Everything works fine, except for the Autodesk Invertor 2017 program, when saving a document, it starts saving at a speed of 1 kb / s , while reading at a normal speed.
What could be the problem? I do not even understand in which direction to dig.