while filming the Sun , suddenly and very quickly the ISS, International Space Station, is flying across the upper part of the Sun's disc from right to left, as seen from a limited area in Switzerland.
This was not a surprise but anticipated.
thanks to www.transit-finder.com you can find out if and when the ISS will fly in front of the Moon or the Sun.
As an extra info, I also double-check with heavens-above.com . If both websites' prediction match, it is very likely to happen.
Observing ISS transit in front of the Moon is easy but in front of the Sun requires a special solar filter to protect your eyes and camera sensor... DO NOT LOOK AT THE SUN WITHOUT DEDICATED SOLAR FILTER or permanent eye damage can occur.
I used a Canon EOS R6 , with RF600/11 lens and x1.4 teleconverter and a ThousandOaks Solar Filter , filmed in 4K60 , then edited with crop-zoom and saved down to HD720 given the extreme cropzoom.
Edited in VegasPro19.