There could be a number of potential issues, the most likely is the pump filter is blocked.
You mentioned some elements have already been replaced so I assume the filter has already been cleaned and you have checked the outlet hoses are not blocked?.
If cleaning the filter didnt resolve the issue it could be a overflow\aqua sensor, to narrow down the fault please advise what is shown on the display, and if any lights are flashing after if failed to drain, so I can determine the error code.
The aqua sensor should be separate from the pump mounted at the bottom, its designed to detect if there is water in the sump so the PCB knows when the water has been drained.
If your not getting any error codes, it would suggest the PCB has failed, as I would have expected the unit to show an error code after the pump runs and fails to get the unit in a suitable state.
A replacement control board would be around £100, however it appears its a discontinued part, which would suggest unfortunately the unit is uneconomical to repair, as the PCB's themselves are not repairable.
The easiest way to tell is fill the washer witha few buckets of water, run the drain programme and see if water is pumped out of the waste pipe.
If there was a pump fault it should generate an error code though, this combined with the fact you have emptied the filter means there is no water in the machine, the PCB should not be calling the pump at all (as there is no water to pump).
I would first find the aqua sensor and see if its open or short circuit, however the fact no error codes are shown on the display would make me think the fault is to do with the PCB\control board.
They are not the same thing, but you normally only have one or other in the machine, as they perform the same task, one works based on a float actuating a switch as water rises, the other works based on pressure.