My bike slid out from under me slipping on a wet grate at a slow speed and the chain got stuck for the first time. Someone I was riding with fixed it pretty easily. It has happened twice more, recently tonight as I was finishing up a ride in the park. I had to stop quickly as some runner on their phone suddenly changed directions. Luckily I was going slowly and I was a block from my apartment. The chain has 1500 miles on it, and I have a new chain I can ask the LBS to put on. Do you think it keeps happening because of something that happened with the FD when my bike initially fell? Should I replace the chain? Should I measure it first and see if it's stretched?