I have the Monoprice Maker Ultimate (MMU) purchased last January. I have generally had good success with the printer once I "finished building" it due to several issues and design problems.
One thing that bothers me is all the files I generate using S3D cause a very large retraction just prior to the start of the print job. This occurs after the nozzle is primed and before the wipe function is executed. It takes about 3" of travel of the nozzle to get any material deposited on the build surface.
The filament is retracted somewhere between 11mm & 13mm
The sample files included on SD card with the printer do not do this, only files created with S3D.
Under the OTHER tab I saw a Tool Change Retraction of 12mm, I set this to nearly 0mm and see no change.
Bill V
Arizona