Sadly, I don't have any Delphi 10.4 licence so I can't reproduce it. I don't see any issue with Delphi 10.3.3 Community Edition, and most older versions (up to Delphi 6) I could try.
But Sakura found the root cause and reported his findings in our forum. He created a QC entry in the Embarcadero Quality Portal, with some reproducing code. We are waiting for a fix from Embarcadero side.
Sounds like if that with the latest commits, we were able to circumvent the problem, while waiting for an official fix in the Delphi 10.4 compiler.
Thanks again Sakura, and feedback from any 10.4 user is welcome!