We’re confronted with some long urls on our mobile website (single page app) where the basket items are placed in the URL as stringified JSON. This causes some events not making it to the Cloudfront collector. For most of the urls this is fixed by find/replace the document.referrer and push the cleaned url to the tracker with setReferrerUrl/setCustomUrl.
However for our single page app, looking at the referrer field this of course does not give the the real referrer but only the TLD (http://www.domain.com).
Currently, single page app events that contain the long url in the referrer (&refr=…) still have a high chance of not making it to the collector.