If the hotend fan is running fast and fine and you already checked bowden is firm against nozzle and does not move at either end, then I normally find a heater/thermistor issue. if you ever remove the grub holding the heater, careful not to overtighten putting it back in, tends to cause shorts in the heater tube which very often leads to a clogging issue. similar with thermistor reataining screw, if the cable moves around the threads on that screw will bite through the cable easily. I file off those threads, makes for a lot less hassle when your changing things around the hotend a lot for solving the cause really need to go through the lot up to and including swapping out heater and thermistor individually until you locate the issue.