I've always fought an annoying thing in #EagleCAD where DRC complained of errors that didn't violate any rules, and searches on the web never turned up answers.
Tried again to search today and found the hidden 'net classes' area which solved that problem.
That's pretty shoddy UI, to report errors, point to a DRC rule, but not indicate that there are rules elsewhere which you're also enforcing.
It would take one little phrase "see net-class rules also" on the DRC dialog.
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