We are having a rather peculiar issue. In my organization we have folders that are available to everyone, and in these folders are various files and forms that people can fill out. For instance, we have a label template that users can open, enter in their data, then print out. Each of these files are marked as "read only." This way, the users can edit the files but not save them.
All users are part of the "Everyone" group in AD, and they should be able to access these files. However, when they open the files, they get this error:

No particular user is specified as having this file open, and it happens to every file on these shared drives. People who are specifically given access per their account in AD are able to open the files and modify them as long as they are given the "modify" attribute. Everyone is able to access the files in their departmental folders fine, as they are given specific permissions to these folders.
We are trying to make it so that people can open these files, fill them out, print them, and then close the file - but not be able to save the changes to these files, which is why we have not given the "Everyone" group modify permissions.
This worked before, but now when people open these files they are greeted with the above error message and are not able to make any changes to it all, not even type in the fields.
When we log in as the affected users through RDS onto the server these files are hosted on there are no problems, and this works as expected - but not when the files are accessed normally through the user's machines.
We are not sure exactly when this started, as we have just gotten wind of this now. It worked at some point in the past, but we don't know when it sopped working.
Any help would be greatly appreciated!