Just updated to 0.54.103957
Noticed that when you walk towards the enemy they do nothing until at arround 220m (ish) then the enemy will start to fire at you.
Then you can literally take a few steps backward and they will stop firing.
Step forward and they start firing again, step back they stop (repeat, repeat...)
It's as if they have a distance cut off point where they can't see you even if you are fully visible.
I tested this on the airstrip.