Ok, so the problem only occurs if I generate the entire terrain at once using Bing? If I then regenerate them one by one, is everything correct?

You have two workarounds:
1. Regenerate all terrains using a different elevation data source.
2. Regenerate all terrains one by one using Bing Maps elevations.

P.S. Thank you for your question. I think this is a critical problem and it will be fixed as soon as possible.

In the screenshots I hope you can understand the problem. When I create the buildings I have the possibility to choose a range for those where the system has no information and therefore does not know the height.
In this case I specified 2-4 as the range.
It's not yet clear to me if it means that he will generate buildings with a maximum of 3 (floor height) x 4 (max range) or 4 maximum units of height.
But in this case it doesn't matter because the result is still wrong.

I tried to generate the buildings both with the "Floow Terrain" option and with " Follow Real World Data", the result doesn't seem to change

The result is that the system writes a number that makes no sense to the building settings and the buildings turn out to be very tall.
Moving them all by hand to lower them is truly an immense and in any case random work.
In many parts the system also generates buildings below the level of the terrain and I don't understand why.

I hope you can help me Alex, thanks a lot

Please explain the problem in detail so that I know exactly what I need to look/do/fix/improve.

I'm again asking for your help for an improvement ... or rather, for something that exists but is not working properly.
I am sending you the geographical position of the area that interests me and also the screen of some parameters.