sounds like the z-axis is getting stuck.

Have you nudged it when it's doing the repest print thing ?

The right hand side of the z/x axis basically just freewheels up the extrusion. maybe it;'s getting stuck ?

It's more likely a g-code and sdcard issue - but you know there are so many things it could be on an ender 3 that maybe hitting it with a hammer every now and then is just a good idea ;-)