Since approx Jan 9, we've had occasional reports of TATA SKY Broadband customers being unable to successfully establish TLS sessions with upload.wikimedia.org.
Different customer locations have reported trouble at different times, with no clear pattern.
Our 'text' loadbalancer that serves wiki content (e.g. en.wikipedia.org) has not been affected, only upload (serving image/multimedia content).
As best as we are able to tell from the debugging data available, there appears to be a misbehaving middlebox somewhere between their customer and our network that is sending TCP RSTs on TLSv1.2 connections.
This is a tracking task, because to the best of WMF's knowledge, there's not steps we can take ourselves to resolve the situation.