Hey there,
when playing multiplayer as a client with friends, most of my flares and fireworks persist permanently for my buddies after been thrown (visually and soundwise, only within their game, not mine). While fast travelling solves the problem, they already grew so tired of this issue (communication is tricky while fireworks are cracking) we decided to ban those supplies from our equipment pool. Which is sad.
In the patch notes of April 2019 the devs stated this issue had been solved and shouldn’t occure anymore… well, here we go. 
Three players, all on PS4 (Vanilla), happened multiple times within the last few days, didn’t capture proof, too lazy to use the template. Sorry! 