Why does the connection with smb mikrotik break?

Question

Computer networks

Good afternoon!
We have a microtic rb750hex in our company, a 128GB flash drive is connected to it purely for exchanging files via smb.
But when copying files > 400MB, the connection is constantly interrupted and the file is not copied to the end. I have already climbed everything I can, I sin on the old version of the smb protocol in Mikrotik itself .. Any other guesses what could be the problem? ps latest update, stable