Smeg DFD6132X drainage fault

Our Smeg dishwasher, model DFD6132X has a drainage fault, it stalls during the cycle displaying an E06 (drainage) fault code, with standing water in the bottom of it. Sometimes if you leave it a while and then try and continue the cycle it does drain and finish the cycle, but not always. I have checked the drain hose, no major blockages, nothing is obstructing the drain pump as far as I can see. I have replaced the drain pump and feeler ntc components and the drainage fault still persists. I am wondering if it is an issue with draining hot water as it will drain after being left for a bit, and the water will have cooled down by then. Any ideas about what to check next would be much appreciated!