I got mongoose whenever I tried to do a strike up through level 40, so I just stopped doing them. Now on vanguard strikes I don't get an error, it just spits me out solo into the strike. Bungie has been ignoring my posts here about it, and it looks like this has been an issue since at least July, with the ongoing statement being they are working on it. That's a long time. Ironically, last night I wanted to go solo a low level strike to do a difficult series of super kills on majors, and kept running into other people inside inadvertently messing up what I was trying to do. That's the only way I can ever get a striketeam, is by happenstance, and this one time I didn't want to. To make things even more ironic, I set my matchmaking to closed to avoid other people for the soloing, and all of a sudden it started putting me in groups! Matchmaking like it's supposed to. Now I'm thinking I'll try closing my fireteam settings and seeing if it groups me. Can't hurt to try.