ITC-306A - E4 and E5 Error

Good morning, I purchased a ITC-306A controller for my 220ltr aquarium. I have two heaters in the tank, one 300w and one 150w. The probes are attached to the back wall of the aquarium one just below the water line and the other down by substrate. The controller has successfully connected to the app.
Settings on app are: temperature units are in Celsius, temperature calibration 0.0C, High temperature alarm value 26.0c, Low temperature alarm value 20.0c, continuous heating time 3hour. I am getting at least two alarms per day (first one around 3.30am-4am!) and others at different times through the day, when accessing the app I am getting E4 error most of the time with the odd E5 error. I switch the unit off through the app and restart and it is happy until I get the error again which usually say in the notification continuous heating abnormal, please check. I have move the probes a few times however that has not stopped the error messages.

E4 means the temperature difference between 2 probes is bigger than 3℃/5℉.
Please understand that we recommend placing 2 probes side by side. The 2 probes are designed for dual protection to identify a probe fault. The controller will alarm if the temperature difference between 2 probes is bigger than 3℃/5℉.
CT (continuous heating time alarm) is designed to remind that the temperature cannot be heated to the target temperature within the time range set by CT, it will trigger E5 alarm. Please check whether the heater can work and heat to the target temperature?