Anet A8 extruder not heating up enough

My Anet A8's extruder is not heating up enough anymore. It gets to 210c seemingly slower than it used to, and once the parts fan kicks in after the first layer, the temperature drops down and Marlin stops the print due to thermal runaway. Up to that point the print quality seems fine. Has worked fine for over 3 years.

I'm using seperate MOSFET boards and a server power supply (problem seems the same when only running the extruder heater so i'm not expecting power to be the problem). Running Marlin 1.1.9.1.

Things i've tried:

• Replaced the heating cartridge
• Replaced the thermistor
• Another mosfet board
• Marlin firmware upgrade
• PID autotune

Any ideas?

Edit: The issue turned out to be the extruder block being mounted too close to the extruder carriage, acting as a heatsink. When I placed the extruder block further down, it now keeps it’s temperature nicely. Ah well, at least I replaced a bunch of parts and my printer hopefully can last some more prints. Thanks all for the suggestions.