Z axis is uncontrollable

I have a Prusa i2 running Marlin on RAMPS

I'm having an issue where my Z steppers can't decide what direction they want to go. Sometimes they move in the same direction, sometimes they move in opposite directions. I've checked my wiring. I can plug in the motors individually and they work fine. I've also swapped out the pololu with a known good several times. This is an issue that's plagued me since I built my machine, but was always solved by a few hours of "rest". Now it seems to be here to stay.

Any and all suggestions are appreciated.

Is your max speed too high? I've seen the steppers do funny things when the speed is too high and they can't spin fast enough. They generally stall and make extremely angry noises...

ok check the pins someone on irc had same problem the z the steppers would randomly move different directions i believe it was one of his pins on the stepper motor connector make sure fully pushed in pins on connector not ramps

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