I would start by saying this, please don't take this wrong. Did you ensure that you put the bow back into spec's? Axle to axle length, Brace height, Cam timing, just to mention a few? Before you took the old string off, did you measure where your nocking point and peep were on the string? Any one of these out of sync and you will have trouble. Plus, depending on the age of the old string, and if you purchased the bow new, the string could have been streched prior to your getting it and setting it up for you.