Tvheadend

How to reproduce:

Create IPTV network (just give it a name).
Add http stream URL, I used a HTTP Stream from another Tvheadend instance e.g, http://xxxx:9981/stream/service/a6203f7176a7e8e30edbf3c01142eba4.

Mux scanning fails and manually playing the stream results in Invalid service message..

2016-04-26 19:51:24.980 mpegts: http://192.168.1.11:9981/stream/service/a6203f7176a7e8e30edbf3c01142eba4 in Test Network - add raw service
2016-04-26 19:51:26.980 subscription: 0945: No input source available for subscription "HTTP" to mux "http://192.168.1.11:9981/stream/service/a6203f7176a7e8e30edbf3c01142eba4" 
2016-04-26 19:51:26.980 webui: Couldn't start streaming /play/stream/mux/7f9d99b0b5d360aa03733735792c957a?title=http%3A%2F%2F192.168.1.11%3A9981%2Fstream%2Fservice%2Fa6203f7176a7e8e30edbf3c01142eba4, Invalid service
2016-04-26 19:51:26.980 subscription: 0945: "HTTP" unsubscribing, hostname="192.168.1.103", client="Wget/1.17.1 (linux-gnu)" 
2016-04-26 19:51:27.982 mpegts: http://192.168.1.11:9981/stream/service/a6203f7176a7e8e30edbf3c01142eba4 in Test Network - add raw service
2016-04-26 19:51:29.809 webui: Stop streaming /play/stream/mux/7f9d99b0b5d360aa03733735792c957a?title=http%3A%2F%2F192.168.1.11%3A9981%2Fstream%2Fservice%2Fa6203f7176a7e8e30edbf3c01142eba4, client hung up
2016-04-26 19:51:29.809 subscription: 0946: "HTTP" unsubscribing, hostname="192.168.1.103", client="Wget/1.17.1 (linux-gnu)" 

Additional testing:

Adding the same URL as a mux to Tvheadend 4.1.1931 results in a successful scan and the stream plays fine.
All access control was disabled during testing.