Why does the VPN connection drop when copying files?

Question

VPN

Given: the Internet is supplied to the local network via the PPtP protocol through a TP-Link TL-WR1043ND v.2 router with one of the latest DD-WRT firmware. There is a "white" IP like 11.22.33.44. Router address in LAN is 192.168.0.1. It distributes addresses to clients in the local area from the range 192.168.0.100-150. There is a file server running OpenMediaVault at 192.168.0.250. Port forwarding is configured on the router to the file server address (on port 1723). On the OMV server in the PPtP settings, the rule for issuing addresses from the range 192.168.0.50-99 is set.
Create a VPN connection on the remote computer and connect successfully. In the explorer, we write the address of the server on the local network and go to the shared resource. A computer running Ubuntu can freely walk through folders, open files for editing and save changes to them. When you try to copy in one direction or another (from or to the server), the VPN connection breaks. If you connect from a computer running Win7 or MacOS X, the VPN connection drops even when you try to view the list of files.
Why is this happening? What's wrong? Already broke his head, because. in the wilds of network settings is not strong.

Answer 1

Raise the pptp server on something else and check how the connection behaves - it will break - the problem is in the file server or TP link (but if everything is ok on the local, only the last one remains), the problem in the OpenMediaVault pptp functionality will not break.