networking – Random loss of write permissions on Windows 10 when attempting to write to an Ubuntu network share 18.04, configuration via GUI

I've therefore shared a few files via the Ubuntu 18.04 graphical interface. I have a hard drive in the Ubuntu machine, ext4, and I access it and write to it from Windows 10. Everything was working fine, I transferred a lot of data, but suddenly I was I have lost the ability to write in any of the shared folders. Windows. After a while, it started working again, but now I have lost the write permissions in another folder! I do not know what to do or think. I receive a message on Windows: Access to the destination folder denied. You must have permissions to perform this action.

I've tried looking in smb.conf, but it does not contain any entries related to the folders I've shared. Is this normal? How do Nautilus actions work?

My hard drive is mounted in / mnt / hdd

The folders are / mnt / hdd / folder1,2 etc.