There were a couple of reports of this bug in the forum but wanted to try and wrap it up so others see it.
Basically, running motherboard firmware 3.1, or any derivative, such as the gen3 5D firmware. can result in a print not being the correct height from the original file. At first, this was attributed to bot assembly errors causing binding on the z axis, z stepper driver not adjusted to correct REF voltage, or the z motor being screwed down too tight causing a bind.
I need to say please check those things first always!
But, this morning, using my Cupcake with gen3 5D upgrade shield and firmware version 3.1, I had a build printing from SD card work perfect for the first print, then the second print ended up about 3/4 of the height it should have been. Hitting reset "fixed" the issue and the 3rd print came out fine.
SO, this appears to be a confirmed firmware bug since even a derivative showed the same problem. My T-O-M running right beside it using 3.0 firmwares has never shown this bug.
Other notes:
3.0 firmware doesn't properly support the ABP function
3.1 firmware does support ABP but has this bug
Hitting reset on the motherboard is a good idea and so far is a workaround for the bug if you must run 3.1 firmware. If you have only an HBP and don't need the belt to move use firmware 3.0.
