The issue with your Irvine ISD roller shade not holding at intermediate positions is typically caused by a worn or malfunctioning slow-rise spring mechanism inside the roller tube. Although you replaced the auto stop part (MRL-A1800), the internal slow-rise spring controls the tension and the ability for the shade to lock at any position. We recommend replacing the internal slow-rise spring specific for Irvine premium RV roller shades. Most models require a 1.25" diameter spring, but please measure your roller tube to confirm. Installing a new slow-rise spring will restore proper tension and allow the shade to stop where you want it. If problems persist, verify that the new auto-stop clutch part is compatible and installed correctly, as improper orientation can affect functionality. You can find the Irvine Replacement Slow-Rise Springs available for purchase on our website.