Another aspect to consider is when you post for help, include your printing speeds, temperature, material and any other pertinent information regarding that specific job. If your print speed is too high for the temperature, you'll get the same results as if your temperature is too low, as the filament moves too quickly through the heater block to reach a good temperature for bonding to the previous layer. When the job starts, and the hot end has reached operating temperature, there's a bit of thermal mass that is transferred to the filament. Once that mass is ejected/reduced, the next extrusion duration may lose the heat soak, so to speak.