Umarex Help with recently purchased Umarex GEN 5 Glock17

Hey all. Just want to preface this with the fact that this is my first airgun and explaining things simply would be greatly appreciated.

Yesterday I bought a brand new Gen 5 g17 from umarex. It was great for a bit, but after dry firing it with no gas or bb's in the magazine to just get a feel for it, the trigger began to become extremely stiff, make a loud click noise when the trigger is fully pulled and sometimes the trigger doesn't allow me to fully pull it. Additionally, after every time I pull the trigger, the slide becomes heavier. When I do cock the slide back, it becomes light again, only to be heavy with the trigger being pulled again.

I want to add that when there is no magazine, the triggers feels perfectly fine, like it did out of the box when I just got it.

Any help is greatly appreciated. Can't return as the box is long gone because I thought it was working.
 
You need to lube the belt inside the magazine. It's the weak part of the design and because the trigger has to rotate it to feed it makes the trigger pull very heavy, and much, much worse if it's dry. I used a combination of moly grease and silicone spray lube. You want to work it in there and rotate it manually several times.