The Ender3 v2 should have come flashed with your firmware.

This would lead me to believe that the Z-Axis is not moving smoothly, this in turn would lead to missed steps on the Z-Axis.
I would re-check your assemble of this axis - Assembly Video Here
It look like you also may have over heated your hot-end filament as it appears in your images.

It would help us if you would post your slicer and its slicer setting.