Theory about Star wars Clone Wars Clone nightmares

I recently re-watched Star Wars The Clone Wars. In one of the last seasons there was a series of episodes of Anikin’s squadron in a siege. One of his troops named Tup eliminates one of the Jedi leaders during a fight against the separatists. Fives restrains Tup and the army retreats. After the battle Tup regains consciousness. Anikin decides to question him but Tup goes into a trance and becomes incoherent. They bring Tup to Kamino to be examined and Fives decides to go with him. Kix (their medic on the squad) runs some tests and he says that Tup had a breakdown. Rex and Fives are confused by this conclusion because they know that the Clones were engineered to withstand any amount of stress. Tup is further examined by Fives and a medical droid and they discover a tumor on his brain(their kill switch for order 66) and decide to remove it. After the surgery Tup looks at Fives and some soldiers in the room after the surgery and says he has been liberated from nightmares he dreams every night. Apparently the nightmares he has each night is something all of the Clones have at night. What confused me is that he was designed not to worry so how could he be scared? What could scare him so much to have nightmares about? There are very few moments in the Star Wars movies and Clone Wars Series of Clones being stressed, or scared. There were many moments when they should have displayed terror but didn't. There was a moment in the bad batch series when Crosshairs and Mayday are walking in a cave. Crosshair stepped on a mine without detonating it. He displayed no fear. Mayday even successfully disarmed it with makeshift tools with no worry even having a small conversation with Crosshair. Wrecker and one of Anakin's clones from the Citadel series of episodes have a fear of heights, not an uncommon fear but still important to gather evidence for a theory. The only moments in the series of the Clones being scared was Rex during Order 66 about to kill Ahsoca and Rex finding out the bad batch did not have their chips removed from their brains. Along with Cut Laquane in one of the first seasons being fearful his family was surrounded by battle droids. So this trend of not fearing death but fearing killing their Jedi leaders and loved ones in danger seems to be the only things that could be the thing they are scared of. Another theory is that they could be subconsciously programmed at night to prepare them for order 66 by the chip they have showing them what to do during the order. The clones are all workers of the military not necessarily soldiers but most become soldiers. The nightmares could just be a manifestation of their stress. Normally people lash out when stressed, maybe their dreams are how their stress manifests. Logistically the Kaminoians could have done this because it is the best time for a clone in the clone wars to stress out during a war would be while they sleep so they can function uninhibited during the day/fight.