A few months ago, all the files in one of the folders on the NC server were destroyed. That is, they are displayed, but when you try to access them, the message “the file is damaged and cannot be opened” appears, then it simply disappears. 1- Could you restore them. 2- what could be the reason. 3- how to avoid it later.?
hello @Ogoram welcome to the forum 
Please use the search - lot of issues have been discussed already
as you didn’t provided enough information nobody can tell what happened and how to avoid it.
- solid backup is recommended so you can recover from software fault, malware or human error.
- by default there are files versions - once the file is changed older copies remain on the server so you can restore them (if you have enough space and don’t configure automatic removal of versions).