ELECTROLUX 318279620A WE HAVE TO HOLD THE DOOR BUTTOM ON TO MAKE VTHE MICROWAVE WORK

You can't, because they are so dangerous to work on. The makers don't publish them.

https://www.fixya.com/support/r29874712-repairing_microwave_ovens

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you may get lucky by cleaning the mica card [protection cover ] this video shows how --https://www.youtube.com/watch?v=jQrz87k973E

You need to dismantle the door.
Unplug it from the mains
Then remove all the screws which hold the door together.
The front should seperate from the inside.
Take care not to lose any parts or dislodge the mesh screen from the window.
Undo the handle from the inside, remove & then replace the same way it came out.
Reattach the sections of the door & tighten all the screws.!

Fuses blow for a number of different reasons. Here's a partial list:
Bad door switch
Door switch sequencing issue
Weak fuse holder
Problem in high voltage circuit

If you need further help, I’m available over the phone at https://www.6ya.com/expert/david_29ad5d1dd86564b0

Replacing the door is one of the most demanding service interventions in the microwave. Substitution is possible only with the original door, otherwise may cause leakage of radiation what is very dangerous.
For identity doors of two different models of the microwave please contact an authorized service center.

Dado

Is it your own or in the rental?
If it is under warranty you may get a replacement, if not contact the manufacturer and they will usually give you a rebate on a new one.

try e spares on internet

When you say stays on , is the magnetron still running ? The door switches need replacement or cleaning or timing went out.