Why might one page not work on a site on ModX Revolution?

Question

MODX

Actually one page does not work - a white screen. If you clear the cache - it opens, but if you go again - again a white screen. Where to dig?

Answer 1

So something is in the process of caching. See what calls are on the page (snippets, plugins), disable one by one, repeat clearing the cache until you localize exactly where it fails.