Initially I was only driving a single SSR for heating. Yesterday I finished all the wiring properly for the fridge, so that now it drives 3 SSRs for: cooler, heater and a fan. I put the BrewPi into test mode to check everything was setup correctly and ran into an issue where one SSR would just switch on and then off straight away. At first I thought this might be down to dodgy wiring, but then after shifting all of the outputs along 1 everything worked correctly.
The weirdly acting digital output had previously been used for just the heater SSR and led to this thread Fridge mode settings advice So perhaps this output was the cause all along? Has anyone else experienced this?