Bug UI cropped using HDRP

Hello all !!
I am trying to crate a test scene using HDR pipeline but I am incurring in a very strange glitch I cannot figure out what I am doing wrong.

Basically, I cannot make the UI coherently displayed on the screen.
Please, take a look to these screenshots:


As you can see, there is a button defined on the up-right corner of the screen that it is cropped, for some reason, in the game view (and obviously also when in play mode).
The button WORKS properly when clicking in the space it is supposed to be.
moving it left and down it will make it rendering properly.
This issue is NOT related to the Scale With Screen Size option because it is reproducible also in Constant Pixel Size and Constant Physical Size.

It may be an issue related to the camera or to my HDRP settings but because I didn't know what I should have looked at, I didn't take any screenshot. If there is the need for you to also take a look at more settings in different part of the engine, please, let me know and I will happily share them !!

It would be very much appreciated a bit of help to understand where the issue is because this will be a deal breaker for me in using the HDRP if it is that broken with the UI.

Thank you very much for your suggestions !!

 

UPDATE !!
It seems that if I change the GameView resolution, the Canvas and the UI updates accordingly.
If I set anything that is NOT a 1920x1080 fixed resolution, for some reasons, the Canvas is NOT stretched to the full screen, as you can see from these images:

I really don't know what I did to cause this issue also because the Canvas is set as Screen Space - Overlay, therefore, I think I may consider this as a unity bug !!

Does anyone have a clue about how is this related to some possible changes I made in the project related to the HDRP or maybe Cinemachine settings?

Thank you !!!

 

UPDATE !!

All right... it is DirectX12 !!!
Switching to DirectX11 solves the problem which, annoyingly, does affect also the builds.
What's the reason behind the issue? I do not know !!!
Help from someone at Unity Technologies would be very much appreciated !!!