"Stepped" Prints - Take a Look

Hi guys, can someone take a look at these pics of my print and give me an idea of what is going on? It doesn't always happen at the same height nor does it have any kind of pattern. Some prints it happens, some it doesn't...the same print. I've replaced the stepper motor and re-flashed the firmware, the belt is not slipping... I'm kinda at a loss.

Well something is coming loose.. and either moving the part (bed shifts) or the extruder

I've checked, and after your post I checked again. There is no mechanical slippage at all. Is it possible that there is a fundamental flaw with how the Ender 3 copes with the G code? Is this a coding error not a stepper motor or board issue?