Sheet-to-sheet slot die coating is a crucial intermediate technique to bring organic and large area electronics (e.g. OLED and Flexible OPV) towards mass roll-to-roll productions. The coating on substrate has to be uniform within nanometers. Additional settings are added to the slot die coater for a better control of the coating bead. Two reoccurring device de-fects were observed and the coatings process was analyzed. The first defect was an increasing layer thickness due to ac-cumulation of coating material to the slot die lips. The second defect was cross directional barring due through bead fluttering. The right speed settings could prevent the defects. Use additional settings to circumvent these coating defects leads to limitations in reproducibility and prevent easy layer thickness adjustments.