After migrating a client's file server from Windows to a FreeBSD samba share, they have noticed some files when opened are not prompting other users to open the file in "Read-Only" mode. The additional users can just open the file with read+write permissions.
This should not be!
Searching the internet gives a handful or results, often met with Microsoft's "Run these powershell commands blindly and you'll be sorted" support method - which are basically no help at all.