Hi there. I am having a very similar problem with my aeg kmk721000m microwave grill too. I get the f134 error and the microwave sometimes clicks on and off and on and off again. I have changed the transformer, hv capacitor, hv diode and the magnetron but still get this problem of random shut down. Did you ever rectify the problem yourself?
I’d really appreciate your help on this if you do have a solution.
Regards