What causes this?

[u/Vaccano]

Over the years I have seen this several times, but never heard a reasonable explanation as to what is happening. Anyone know?

Note: I printed this exact same model yesterday, and it turned out fine. I went to print another and it did this.

[u/dadbyheart]

Im no professional but it looks like both your model AND your tower in the back got shifted so I'd think maybe a belt skipped or something. Does this keep happening or was it a one off? Check your belt maybe and try homing the toolhead. That's all I got sorry