Having trouble to reproduce it now, too. It either occurs only by chance and I was lucky before or you fixed whatever caused it. The difference between Saturday and today are a few updates and a new launcher... So I want to conclude it's the second option?
We need more people to report it just in case it happens again.
Went Afk for one hour to shave and take a shower and told people to whisper and invite me in the meantime. I recieved just one whisper and nothing else; no invites, no whispers.
It already happened like five to ten minutes after i went afk to shave (came back to see if there was a server crash to restart the afk test).
Seems to be fixed for everyone but the host. A host can only change his position, but never unselect his slot in PVP.
Not even if the host is in Team 1. Is there a rule for this? Or a boolean that says "lock those things for the host" ?