Error F05 indicates a jammed pressure switch. The machine gets a signal that it is filled with water to capacity and therefore won’t spin. However, it is not always so.
Normally, the spinning starts once all water gets out of the drum, so the spinning will be safe. The error occurs when the signal is not reaching the destination point.
Most likely, there is a problem in the pump or filter (a blockage). However, in this case, there should be a good amount of water in the drum when the error appears. In any event, the error requires a bit of troubleshooting.
If there is no water in the drum, and the error is still there, the pump has nothing to do with it. Probably, there is a pressure switch problem (possibly, physically blocked), or the air pressure chamber bottle won’t let it function properly. Then there will be pressure in the tube, which connects the pressure chamber bottle with the pressure switch, and it won’t let the switch release. To check this, pull the small tube off from the base of the pressure switch. If you hear a click resulting from a sudden release of the trapped air, and the switch jumps back to the off position, it is due to the blockage by the pressure chamber bottle. Not unlikely, the excess air will slowly get out over time.