In ConcreteCMS 9.4.8 (Japanese version), a blank page is displayed instead of an error message for non-existent URLs

Well in that case, I am afraid you must either get the theme modified to prevent the numeric url appendages and force a 404 or learn to live with the theme as is.

I’m always so sorry.

It seems like improvement is unlikely.

Even with a subscription, the creator hardly ever responds, so it might be better not to buy it.

Thank you for your trouble.