Loris

Another important think: with "Use MSBuild externally to compile" = TRUE the debugger become not usefull because all the breakpoints on the source will be ignored!

Hi, I have the same problem. Partially solved. Add here information maybe usefull for others. [dcc32 Fatal Error] GestAggiorna.dpr(80): F2084 Internal Error: AV09BA3340(09B80000)-R00000018-0 After installing 10.4.2 over 10.4.1 I have the problem any second time I try to use the debugger. To solve I need to close and re open the IDE. But this is not a valid solution. The problem happen with many projects previously used with Delphi 10.4.1 without problems. But with started new project, simple project, with Delphi 10.4.2 there was no problem. Using the suggested: "Use MSBuild externally to compile" = TRUE Solved my problem, but need also this info: need to remove the file CFG and DOF files. I found that I have in the source folder the CFG and COF file that was used with Delphi 5. The MSBuild show message about "the project seem to use old packages..." Found that CFG and DOF files was copied from year to year passing over many Delphi versions. Only today they were deleted. Finally: I need to keep the "Use MSBuild externally to compile" = TRUE Note: with "Use MSBuild externally to compile" = FALSE the problem of second time debugging is still present.