Holes and gaps in the top layers Increase the number of top solid layers to reach at least 0.5mm thickness.Increase the Infill density percentage to prevent hollows in your print that allows the top layers to sag.Perform Under-extrusion troubleshooting. Related articles Hotend Cable Positioning Grinding Filament Stringing/Oozing Replacing a Thermistor Printhead cables positioning - Bowden and Cable