Chain comes off during tightening phase of calibration

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This thread has a number of suggestions from others who had the same issue:

Chain jumping off on "Pull Chain Tight" calibration step

Hi All! I have been trying the step where I run the chain over the motor and connect to the right side then pull it tight. The problem I keep having is it is jumping off, even when I hold onto the chain at the right side. I am up for any suggestions on this step or an alternative method.