pollackscience

Forgot to mention, my CR10S Pro V2 is running firmware 1.70.0, so it's been a bug before 1.70.1 was introduced.

I have the same issue with a CR10S Pro V2. Like others note, the issue seems to be with the call to "M420 S1 Z2". According to here (https://marlinfw.org/docs/gcode/M420.html), this command enables bed-leveling, assuming there is a valid leveling mesh. On my machine, this command seems to start a bed-leveling procedure, then the next couple lines are executed incorrectly and the triangle is drawn. If you replace the "M420" command with "G29" (the command to perform a new ABL), the ABL runs and then the correct vertical lines are drawn instead of the triangle. Maybe the M420 command is executing incorrectly because it can't retrieve a valid leveling mesh? How does one load the ABL that you can perform from the "auto-leveling" settings?