Permission troubles with SMB NAS (raspberry pi)

Hello community!

I have configured a homemade NAS using an external HDD and a Raspberry Pi. I use 2 Macbook Pro laptops at home with El Capitan 10.11.3 and an iMac 27 with the same OS version at work. I can connect to my NAS either at home and work but te problem occurs at home. From a remote connection I can acces without any problem and I can modify, move or create folders or files, but from local I can't do all these things. When I try to create a folder or to move a file, the system reports me a message:

ENGLISH: The operation couldn't be completed. There was an unexpected error (-50)

How can I solve this problem?

Thanks in advance

Salus