my chain seems to be tight as I roll the wheel and then it becomes loose if I continue to roll it. when I am riding it seems to grab as if it was not catching all of the teeth on the front sprocket. The wheel seems straight and the rear sprocket does not appear to be worn down or misaligned. the chain was cleaned by a racer and lubed as well. I recently cleaned it after the problems started happening and lubed it as well. any help?