Document and support it, or create a version that you can document and support.
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I'm not sure of the exact threshold, but I've had cases where handfuls of databases are completely skipped on systems with > 255 databases.
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Of course I don't expect a fix to an undocumented procedure, but I've had to write my own, which I've found much more reliable, so perhaps Microsoft could consider doing the same and making it an official part of the offering.