If the chest pads have a hard time making a solid connection to the muscles, first add some extra water to the pads.
When tightening the vest section of the suit, make sure the shoulder straps are loose to start. Then tighten the side straps of the vest (all four on each side, from lowest to highest). Then, pull the shoulder straps down as tightly as possible, while still allowing a comfortable range of motion. This should fix the issue.