I think I might have found a MODx type bug, althought not totally sure!
I'm using <base href="[(site_url)]" /> in my head tag because Ive enabled fURL on MODx.
When I'm caching my checkout page Foxy is caching what seems to be the index.html page (some times more then once) then caching the checkout page and what you end up with is a complete mess. Or worse a blank page.
When I check through the cache code, I can see a mix of html and css for index.html and /store/checkout.html.
I can't work out if base href="[(site_url)]" of MODx, delay in changing a MODx template to foxycarts caching of them or the cache storage of template in foxycart not clearing.!!?