Hmm, it's strange that it's just happening on the one ESC, so either it's a setting issue, or that ESC has a hardware fault.
Could you hoot kit up to blheli configurator to check all the settings are the second.as the other working ESC? And also of its the same firmware running on the suspect ESC?
Also another thing worth checking if you can swap the suspect ESC to another motor output on your FC so see if it's the motor output or the actual.esc causing an issue. Sorry to suggest so many things, but we spent a lot of time making sure the chaos ESC are as close to perfect as possible and only have had 1 or two.faulry ones.
But if it's faulty we will replace for you