when your cloaked you generate clicking noises. also when you are at half health you bleed. every few seconds a blood splat hits the ground.
This can give away your position. if your cloaked this is even worse cause the way the cloak works is it uses the environment around you and distorts it around you. That includes the blood you just splashed on the ground and now there is a bright green target on your chest or leg.
Further more regarding your blood. if a fire team member shoots at you while cloaked and just barely taps you. There will be a blood spot on your body that is bright and clear as day. it doesn’t go away right away. You can uncloak and recloak and it will go away. Sometimes it glitches and doesn’t go away at all and there is this bright green target painted on you that stand our no matter were you go and you got to uncloak and recloak to make it go away.
also if your cloaked you can stand still for a few seconds to become completely invisible. This can be helpful.
You also just got to chalk it up to people who have a far more observant eye. Some people can just pick you out super easy and others (example me) couldn’t find you if you were standing directly infront of them doing the macarena. So just always expect someone like that and test your luck right off the bat and see if they do notice. if they do then you know you will have to be more stealthy.
Get out of the trees, use crouch to get into position that is in their field of view, take a few shots and get out. Never engage at half health and believe and think they can’t see you cause your blood will reveal you.