We run a big Discourse based community, similar to this one and we utilize CloudFlare for caching capabilities.
Over the last couple of months we have been receiving complaints from Telia internet customers that they are experiencing slowdowns and 500-errors on our site. I have been able to reproduce this on my smartphone, which has a Telia SIM. The issue has not been reproduced on other major operators of the local market.
It seems that the issue could be worked around by disabling CloudFlare’s caching, thus losing all the benefits that comes with it. We have reported this to Telia, but they are not very interested in investigating and point their finger at CloudFlare.
Our site is in the Finnish language only, so it is very focused to Finland geographically. I am hoping CloudFlare staff could have a look. Telia is one of the bigger operators out there, locally and globally.