I'm trying to replace the R2 mainboard with a ramps/mega 2560 board pair. I have all 3 steppers connected to the ramps board with their end stops. I'm testing using the pronterface ui. When I first connect to the board and drive either the x or y stepper, only the Z motor moves for a short distance, it stops, then the respective X or Y stepper works correctly. I'm have been working with customizing the arduino code to work with the original R2 hardware using the new mega 2560 card. I've become fairly familiar with the arduino code and do not see anything in the code that would explain the behavior. Right now everything is removed from the printer and connected on my work bench which might be related to this problem but since the steppers work with both pronterface and pronsole programs ??? Has anyone seen this behavior elsewhere? Any thoughts? Thanks guys.