Incomplete or overlying layers

[simone_ferrero]

I'm new in 3D printing world, so sorry for my mystakes or my ignorance. My printer is doing crazy things: i attached some photos of my last printing session were you can see a personal upgrade I was trying to print.
Three days ago I installed a new firmware version downloaded from this forum (here's the link viewtopic.php?f=20&t=19846) because I replaced my board (GT 2560 Rev. A+) with a new one. I fixed only the z step/mm, different in my configuration and everything was working while I tried to print something. I use ultimaker Cura as slicer and I noticed everytime I open or close the program, marlin reboots oh the printer, but the worst problem is ALL the layers are printed very bad. Some are incomplete, in sense the extruder prints the outline of the model but it 'wrong' the infill or the inner shape. Everytime I try to print again, the model comes worst... as you can see in the photo, layers are not sorted, specially the inner holes. Please, help me!

PS. I attach the firmware, some photo of my last session and the .stl file.

[Gingko]

Try to measure the voltage of A4988, motors can run stable with 1.0V or 1.1V.

[cyhofim]

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