Blowing fuse problems

Hello,
Actually my oven is a MIDEA brand (whatever no name brand that is) and the problem is with the mains fuse. After I repaired some contacts problem that prevented the oven to start microwaves when I close the door (the contact wasn't turned) now I have a problem with the fuse. It blew up after one day of the initial repair. I have dissasembled the oven, done a quick check and replaced the fuse. I've done some testing, all seemed to be ok, the oven worked properly, no fuse blowing out, no nothing. After some hours, next day when I tried to use the oven the fuse blew again. Once again I've dissasembled the oven, did some checks - all ok, oven working - next day the same :). The fuse blows when I open the door, in the same moment. After I change it I can power on the oven, all works, but after some 15-20hours when I open the door the fuse blows out instantly.
Could anyone help me. I have all the tools and can change components or other stuff, but my field of expertise is laptop and desktop repairs not ovens.