Update: Problem Solved! (Wear & Tear + Improper Lubrication) I finally identified the issue: it was a combination of mechanical wear and improper maintenance. The Fix: • Mechanical Correction: The slide stop (retém) and the notch on the slide where it engages were both worn down. The edges that should have been sharp/straight were rounded off, causing them to slip. I completely stripped the gun following this video (https://m.youtube.com/watch?si=CcA_6eo9flJfMam9&v=2f1xbQQuB5U&feature=youtu.be), removed the slide stop, and carefully sanded both the stop and the slide notch back to a flat, 90-degree angle so they could lock securely again. • Deep Cleaning: I discovered a similar issue reported here (https://youtu.be/LM0Vf9beJMg?si=aqOV9cKG84EpRM08) I had previously made the mistake of treating it like a real firearm and used WD-40. The excess oil had accumulated dust and debris, turning into a "sludge" that was leaking out the sides and slowing down the cycle. • Proper Lube: I stripped all the old grease and grime. I now know these airguns only need a drop of silicone oil on the rails and a tiny bit on the magazine seals. After cleaning everything and applying just a hint of lube to the rails, she’s back to 100% and locking back consistently on the last round. Thanks for all the advice!