Hi, we have a BigBox Dual and were very satisfied with printing quality at first. Now we are getting weird problems with the z-axis: Sometimes in the middle of a prints, some layers are about 10-15% too high. Not all layers are affected but the overall size is of by up to +10%. When looking close one can see a little difference in the surface of those layers. We do not know were this error comes from - what could be causing such behaviour??? It could be related to the use of support material because it seems that layers that contain support material are more likely to be affected. I currently suspect that the z-axis is loosing some steps while its making those minimal movements for correcting the bed-level; or that the tool-change (which occurs outside the leveled bed) introduces some z-axis error - But I do not know how to test or confirm those assumptions... please help! We print with ColorFabb XT in Tool1 and use HIPS as Support-Material in Tool0. As Slicer we use Simply3D. We have to level the bed quite often - most of the time once before each print. It seems the IR-Sensor is very dependent on ambient light (we have very large windows in the room the printer is working). Our Tool change scirpt: ;always use T1 so X values dont change T1 ;Dock G1 X75 Y200 F3000 G1 X75 Y230 F3000 ;move some millimeters to avoid bringing back burned material G1 X82 Y230 F3000 ; change to new tool [new_tool] ;Undock G1 Y200 F3000 Our Starting script: ;BigBox Printer Start Script Begin ; Set Tool Offset M218 T0 X-35.0 Y0.0 M218 T1 X0 Y0.0 T1 ;Homing M117 Homing. G28 ;Dock G1 X70 Y200 F3000 G1 X70 Y240 F3000 ;Prime Extruder 0 M117 Prime Extruder 0 T0 ;Select Extruder 0 G92 E0 ;Reset E G1 E10 F200 ;Extruder 10mm G1 E-1 F200 ;Retrtact G92 E0 ;Reset E ;Prime Extruder 1 M117 Prime Extruder 1 T1 ;Select Extruder 1 G92 E0 ;Reset E G1 E10 F200 ;Extruder 10mm G1 E-1 F200 ;Retrtact G92 E0 ;Reset E T1 ;Undock G1 X80 Y240 F3000 G1 X80 Y200 F3000 M117 Print Starting. ;BigBox Printer Start Script End Thank you for your answers!