When one hand is at full extension delay beginning your pull until the other hand completely catches up to the leading hand. Instead of having one hand overlap with the other hand (like giving yourself a hi-5 to the back of your hand) instead keep the hands in line with the shoulders. Only your thumbs should barely be able to touch each other if you’re sticking them out. Basically it’s not important for the hands to physically touch each other, it’s important for one hand to wait for the other one to catch up before the pull begins. Catch-up drill can make breathing a little difficult sorry.