Having issues with my brand new Debut Carbon Evo

My old hand-me-down Onkyo CP-1030F finally crapped out and I decided to buy the turntable ive had my eye on for a few years now. I got it from Amazon and it came pretty quickly. I set it up pretty easily despite the EXTREMELY overly-simplified instructions. I made a stupid mistake and put the 78rpm belt on at the same time I had the flat belt on, gave the sub platter one half-turn and the 78rpm belt snapped. Okay, bit odd but I get it, my mistake. I dont have any 78rpm records anyway so i dont care. But since I started using it, its been sounding pretty wobbly, with the music slowing down and at one point the turntable came to a complete stop. I lifted the platter and saw that the pulley was still turning freely with the belt just sliding over it like nothing, sub platter not moving at all. I readjusted the belt and all seemed well but soon enough it started happening again. My guess is that the turntable (being that its an old model) sat on a shelf for a few years and the belts dried out, hence the 78rpm one snapping immediately. So im buying a new belt, a silicone one that should last longer, but what if that isnt it? Just frustrated. My old turntable was like 50 years old and I never had any issues with it. Anybody have similar experiences with the debut carbon evo?