Press rear windscreen heating spoils radio reception

[notorious]

Another question:

When I engage rear windscreen heating by pressing the button on climate I hear hissing sound from radio. Seems like reception quality becomes poor during heating.

I know about 4 antennas in rear windscreen and diversity switcher. Is something wrong with them or is it normal to lose some reception quality during heating?

If it's abnormal, where I should look first? Diversity switcher?

Thanks.