Slow Motor at take-off

the other day we were doing flights with our octocopter: the first flight went all right and the drone behaved well, but at the take-off of the second flight an engine didn’t spin, while the engine placed on the same axis seemed to rotate very slowly.
I am sure these are not problems related to the calibration of the ESC, since it has been done and checked several times and several flights have also been made.

I attach the log:

Thank you for your help.