no the cogging shouldnt have anything to do with it because when you first start up, whether the fan is on or not, it is at room temp.
You might have a short or wires connected wrong. Please upload pictures and exactly what kind of motors and battery youre using.
Also how did you diconnect the fan? did you formally open the esc and un plug it? or just jam something in the fan blade? (sometimes people do that lol)
Also when i used to have 270kv motos on that esc. when i pushed the throttle all the way down right away, the motors would cog up big time, i had to accelerate gradually (which is how you would accelerate when driving anyway) is this what youre talking about maybe?