S4C+ controller restarts automatically during ftp

Simotion

I have an S4C+ system that I connect to by the ethernet service port.
I use an FTP-client (filezilla) to transfer files from and to the controller.
When I transfer large quantities of files sometimes the connection gets lost because the robotcontroller restarts by itself.
For small quantities like a programm file there is no problem.
And now I wanted to transfer a new system with Robinstall and during transfer of the system, the same thing happens,
the controller restarts by itself and the connection is lost.
During that 'automatic' restart, the restart does not get finished, it stays in its startup phase endlessly, so only solution is to power cycle the controller.
Does anyone has simular experiences? Any solutions?