ISSUE:
Proximity/Radio voice chat can be toggled while cycling through various menus in-game such as the Arsenal menu, inventory, placement mode, and more.
REPLICATION:
Not hard, really; just go into different menus and press L1 for any reason. L1 is the default button for both cycling pages left in menus and for toggling voice chat.
TROUBLESHOOTING:
Just press L1 again. That's it. This is a very non-obtrusive bug, but I am reporting it simply because it exists.