<p>I've applied <a href="https://github.com/openstreetmap/openstreetmap-website/commit/d53bbe53f48d3f235ebc93af665ac912c057a51b" class="commit-link"><tt>d53bbe5</tt></a> to disable caching for CORS responses, which should fix the problem although it's rather ugly and I'm not at all clear that there shouldn't be a better solution...</p>
<p>The interesting thing is that the <code>304</code> response doesn't actually carry the CORS response headers so the browser couldn't use them even if wanted to. They are getting returned from the ruby part of passenger to the C part though, and I don't think the C part is eating them, so I think the apache core must be discarding them for some reason.</p>
<p>In any case I have been unable to find any discussion anywhere of how CORS and caching and conditional gets are supposed to interact so I really don't know what <em>should</em> be happening here.</p>
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