Can't copy two files at the same time .. Interrupted functio

Hello,

when I try to call a big file (~50MB from server) and at the same time a
smaller one … the first
copy aborts with the popup message:

ERROR reading
/Server/download … → the 50MB file
Interrupted function call

The file at the target machine is then completely removed. There are NO
other applications running on the system … only fs-cifs has been
started.for connecting the server machine.

What’s the problem ??

Armin