I'm not sure if it's supposed to be like this or it was intentional. In the latest plus, I've noticed that the tab chat behaviour is different. I'm not sure how the general rule works, but say I click Tab 1 when I'm on Tab 2, and then go to a different window such as Firefox, then back to messenger. It's back on Tab 2, rather than Tab 1. Which can be very confusing
Cheers
tom