Heating/ventilation system has broken down several times

Hello everyone, last fall we moved into our new building,

Installed is a Vitocal 200-A in combination with the ventilation Vitovent 300-F.
By now, the ventilation system has been defective several times and the heat pump once.
Just now, the heat pump is showing a fault again.

Our heating engineer is committed and reports the error directly to Viessmann, but the customer service always takes a long time to respond (several days for the heating system, up to several weeks for the ventilation).
Then some parts are replaced, and after that, it runs again.

Of course, I have concerns about how this will be in the future, especially after the warranty expires.
So far, apart from the inconveniences and wasted vacation time, I haven’t had to bear any costs at least. Of course, it’s still annoying.
At the latest after the warranty expires, I will be left bearing the costs. I simply suspect that the heating system will not get any better and something will constantly fail.

So, to cut a long story short, here is my concrete question:
How often do I have to accept a repair (due to different faults)?
When can I demand a replacement? Can I even do that?

Well, one wonders what was broken there... and which parts were replaced... perhaps you have a lemon.

When I mentioned the word "Monday model" during the last technician visit, the colleague didn't like that very much^^

So I know that the mainboard in the ventilation system was replaced 3 times because of different errors. Allegedly, this is a standard procedure...

Unfortunately, my wife was present during the heating service, she could only tell me that something was replaced. Unfortunately, you don't get a report.

Yes, of course that is a standard procedure nowadays. A diagnosis and replacement of the defective cent-value components on the circuit board costs more than simply installing a new one.

Perhaps a component is undersized, or there is a design flaw, and so possibly the same thing always burns out. (Just like the same errors in the first generations of LCD TVs)