deepcat:"Classical mechanics stubs" reports correctly, but randomly reports zero.
'CatGraph could not find the category 'Classical_mechanics_stubs'.
The following reproduces the problem:
deepcat:"Classical mechanics stubs"
deepcat:Physics
deepcat: "Disambiguation pages"
deepcat:"Classical mechanics stubs"
And then these also begin to do the same (begin to report zero)
deepcat: "Optics stubs"
deepcat: Physics
And then this fixes "Physics", but not "Classical Mechanics stubs"
deepcat: "Disambiguation pages"
deepcat: Physics