There is a bug in PUBG relating to squads. Sometimes you'll have a squad member who isn't listed as a squad member but if you shoot them you get the "Friendly Fire" message. I had this on my very first game a month ago - but in the last day its happened a few times.
One time, a squad member who was in my list - kept shooting me. At first I thought he was just an idiot - but I think it was I wasn't listed as his squad member to him.
Makes squads difficult when you don't know who's on your team!
thanks for pointing it out! Please use the feedback function of the mobile Stadia app to report your issue directly to the Stadia team.
I had a trio going with my brother and his friend, and my brother said i didn't show up as friendly for him, but his friend and I had no issues. Luckily he never shot me because of my bright red stadia gear.