@theluthier I found the stray dog, I’m afraid I was too late, had to put it down.
Found it in the swing frame file, when I did the hydraulics I originally had the collection in the chassis file and then moved it into the swing frame file after I finished.
I went back to the master to see it was now zero users but still had the error.
So I did what you said in the live stream, I added a cube and allocated the material to it and shift x’ed it in the material panel, saved the file and reverted it and hey presto, vanished , no errors.
