The sliding splash guard on the lid is just that- a splash guard to prevent minor spills when the road gets bumpy. When gravity is in play, liquid will still trickle out from the underneath the slider. Now if liquid is escaping from around rim, that is a different story. The gasket around the circumference of the lid is absolutely designed to be water tight, so if it is leaking from there check to make sure your gasket is still evenly wrapped around the inside of the lid. If the problem persists, let us know and we’d be happy to send you a replacement.