I see a similar issue in some EX4550-23Fs here.
A client has 4 of them in a ring, and we can see the exact same problem. This is with 15.1R3.
Suddenly, the switches start deleting and re-learning mac-addresses. This seems to last for a few hours, causing all kind of isses when traffic to the deleted mac-addresses is flooded on all ports/vlans before they are re-learned.
And after a while, it just settles by itself.
Did you ever find out anything in your setup?