F9 almost always indicates a door switch fault. (In some models F9 with another letter behind it means something else entirely).This is usually caused by either a bad door switch, a loose door switch mount (which are pretty simple problems to fix) or occasionally a problem on the control panel.Even though a door switch clicks, it may still be bad inside. Its continuity must be checked.Door switch or mount trouble can be caused by slamming the door or by opening the door while it's cooking without hitting the Stop pad first.There are plastic mounts inside the microwave which hold the door switches and onto which the door latches lock when you close the door.The screws on these mounts may be loose. If they get too loose, the switches will not be activated properly.Sometimes it's a broken tab on the switch holder, allowing the switch to rotate just out of position. This tab can be hard to see, since it is under the bottom edge of the switch.One test that sometimes helps is to gently lift up (and/or push down) on the door or handle as you try to start it. If it works or tries to work, then it's a door switch mount or door alignment issue.
If this answers your question,click accept as this is how we get paid for our knowledge.Need more info ask.bonuses appreciated. note;As I am not there this is based on your observations and information.