User has recently been updated to 18.5 (on Windows 10 x64) and has begun experiencing a bug where existing files open as Read Only. When this occurs we have observed that InDesign is not consistenly creating a lock file for the document. If we close the document and reopen it, it will open as editable and the lock file will be created. User had not reported such issue prior to version 18.5. Project files are being stored on a SMB share and no other users are accessing the file when the issue occurrs. We've also verified that the user did not have the preview pane enabled in file explorer, and the share permissions are set correctly.