It was in before 2.2 I recall there was a pretty strong thread on here of CMDR feeling aggrieved about the game curtailing their play-style by not allowing them to keep a lot of open missions (mining, combat, hauling, smuggling, etc, etc)
I ran into this pre-2.2 but it looks like they might have decreased the number of missions in the latest update. I was going to try some long range passenger missions but keep getting the "Too many missions or contracts" error even though I only have 5 open missions. I'm curious if they put a limitation on the max value of missions or if I'm just running into a error. The missions are available, I have the minimum cabin class and a passenger space but I can't take on any new missions even after a log out, log in and trying a different mission. I also cancelling a mission and tried jumping in and out of the system but am still getting the error.