I have exactly the same problem than Lajos Juhász in Alexandria 11.1. I did only use the RadServer template. So it is not something to do with my code or large project. As soon as I change something (I change a comment), then I get the internal error. I did apply 11.1 Update 1 patch but it does not fix the issue. I did also install the patch for people working in Windows 11 (I am working in Windows 10) but it does not help.
Note that there is a Defect (RSP-37631) entered in https://quality.embarcadero.com/
I do suspect that it has to do with Visual Studio installed on the same machine (I have Visual Studio 2019). I have seen this in the quality portal for related defect.
Could you (@Lajos Juhász ) tell us If you have Visual Studio installed?