I've run into an issue with jitsi while playing with xcap. The server (running Kamailio at openrcs.com) was configured to close the connection after replying to HTTP requests for XCAP operations. Most of the operations worked fine.
From the server, after the first request, I challenged for authentication (401 HTTP reply) then closed the connection. I could see on the network that jitsi was sending on the same initial connection (I guess because writing fast before getting broken pipe), but then created a new one and sending again -- all working fine at the end in such cases.
Only for new contacts, when jitsi tried to upload the contact on the xcap server, it didn't work. It displayed a box saying that were errors communicating with the server.
I haven't dug further, but could be that GET operations are fine with broken pipe, but not PUT. I solved by not closing the connection after 401. However, I just wanted to point to the devs, maybe there are different connection handling for these two cases and the PUT operation needs to handle more error cases and make it work for connection closed cases.