I couldn’t get a picture of when it happened, but some things that happened while trying to replicate:
Undeletable, unmoveable chord.
Also, the chord names appear to be overlapping each other when you rapidly press on the piano:
After moving the measure remover to the left, this happened:
After accidentally clicking on the “Remove this line” button, this happened:
Moving the last chord results in a glitched highlight:
TL;DR: Don’t spam the on-screen chord chart on the last chord of a line, or bugs.