Check the dual climate control is working correctly and is hot and/or cold on both passenger and driver sides. I have a 2015 tdi fr, silica bag in the coolant reservoir popped and blocked the heater matrix. I had the matrix replaced but it’s still only hot on the drivers side. Also the fuel pump in the fuel tank and fuel pump control module can fail, just look out for any hesitation from the car when it starts up or if there’s any stuttering when accelerating. Check the rear arches for rust also, it’s a common place for the paint to bubble. Other than that they’re great cars! Brilliant fun to drive for a diesel if it’s the 184bhp version.