Getting Randomly Matched While On Invite Only

[(XBOX)NotCypher3106]

So, yesterday my friend and I were out on the Plains Of Eidolon doing bounties. We had just taken another bounty when the series of events started. We enter the loading area to enter the Plains from Cetus like normal, except this time he remarks he's lagging worse then normal. Then, his game completely crashed. This was irritating, because it meant I needed to stand around and wait on him to get back in the game before we could do the bounty. Now, let me state once again I was on Invite Only. In fact, I only ever play Invite Only or Solo, and was at the time appearing offline. Yet, for some reason, while I'm waiting on my friend, a random player gets in the game. One I've never met, nor had he. Soon afterwards, within about a minute, a second random player joined my Invite Only game session. It was at this point I aborted the mission, as I only wanted to play with my friend, not random players, and waited as I loaded back. When I got done loading, I immediately paused the game, and sure enough, I was still on Invite Only. My friend, for clarification, also plays Invite Only or Friends Only. 

[(XBOX)xRufio13x]

I play solo, and it matched me 3 times in the plains with randoms. I think to get around it, you have to set it to invite or solo, then play in the plains, but if you leave and then try and go back, you have to set it to invite or solo again, even tho it technically says "invite only" or "solo". It's been working for me.