Sharpen AI Maximum Resolution

Quick question: I’m just wondering if there’s a maximum input resolution for a photo to be processed in Sharpen AI? I’m processing some old “Instamatic”-style photos which have been scanned (not by me) at a very high resolution of around 15000 x 15000!

Trying to use Sharpen AI results in no change whatsoever. However, if I reduce the picture to, say, around 3000 x 3000 and then use Sharpen I get excellent results at the new resolution.

I’m using v4.1.0 but the behaviour of the previous version was the same.