Hey guys. I had a 2x7 road bike and I decided to upgrade everything on it. So I changed the wheels and put on a full tiagra 2x10 groupset. The components were 2nd hand but not bad condition, however it was missing a chain so I put a new one on. On the stand it was working fine but when I was riding it, the chain was slipping. My colleague said its because of the cassette is too worn so I was like fine, I bought a branf new tiagra 10spd cassette and fit it on. And now I still have the same problem. Even if I dont put pressure on the chain, just riding it normally it's slipping. What could cause the problem?