Swift 3 HDMI suddenly broken

Hi there,

I purchased my Swift3 just some weeks ago and ever since I have used an external HDMI monitor.
Well, I now got a new monitor an attached it. For the first time, everything fine.
Shutdown, after lunch started again.
Now.... terrible screen flickering, distortions, screen goes off and on again.

At the first time, the new monitor worked fine, right after lunch and staring the Swift3 again, the trouble has started!

I tested the new monitor with a different computer and same HDMI cable, everything fine.
Thus, the new monitor is proven to be fine, even using the old hdmi cable.

Now, attached the old monitor to my Swift and now the same symptoms!

In other words, no way to use an external monitor any longer with my Swift3 :-(

Before contacting the support, do you guys have any more ideas?

Would you try a different cable, although the cable works with different computer?
I don´t want to waste any money for new cable that might not promise to help....

Thanks!