Some possibilities could be... A Z2 on purpose somewhere, a Z2 when you meant to do a C2, a Z3 instead of a C3 and so on. A possible loss of connection at a point where the position didn't get matched between the control box and software. I have also seen where the previewer was used and then going from that right into cutting a file has given the wrong location. That was addressed some time ago though, so unless you are running an older version, that shouldn't happen.
What is your shutdown routine? Always close the software first, not the control box.
If guns kill people, I guess pencils misspell words, cars drive drunk and spoons make people fat.
"Those who hammer their guns into plows, will plow for those who do not" - Thomas Jefferson