Photoshop thinks my external scratch disk is same size as my local drive
I haven't found anyone else online experiencing this particular issue with scratch disks. Hope someone can help.
I have approx 300gb free space on my external drive, and am using it as a scratch disk. Now Photoshop tells me the scratch disk is full, and when I see the list of disks available, it shows *exactly* the same free space on the external drive, as my local drive (also on another partition).

I have tried,
Rebooting the mac and Photoshop,
Reinstalling Photoshop both with saving my settings, and a complete clean reinstall all settings deleted,
Running first aid on the drive,
Restarting the drive,
Nothing helps.
