Synology NAS - I have to relink all folders every time I start Lightroom Classic. Why?

I am using a Mac and have a Synology NAS connected via ethernet. My RAW files are stored on the NAS and my Lightroom catalog is on the hard drive of the Mac. All of my folders appear in the Lightroom folders tab and when I click on a preview image the image appears.

However all of the folders have a question mark icon over them every time I start Lightroom (a couple of hundred folders at the moment). As soon as use the 'find missing folders' function for one folder - they all instantly appear and the question marks dissappear. I can then start editing.

This happens every time I start Lightroom. Lightroom is pointing to a parent folder on the NAS and in Lightroom the path appears to be correct - i.e. //ServerName/FolderName.

The NAS is always powered up and I have no network issues. When Lightroom is displaying this behaviour, I can access the NAS from many other applictions on the Mac and also from other devices e.g. Plex on the TV.

Can anyone help solve this behaviour? Thank you.