Hi ,
I apologize for the delay in responding to this post. Is this something that is still a problem for you? We have started looking into potential causes and solutions for this issue, but we were wondering if you might be able to provide some additional files that would help us determine what is happening.
If you could provide the UnrealHeaderTool log file, which is located in your Engine directory at Engine\Programs\UnrealHeaderTool\Saved\Logs\UnrealHeaderTool.log, as well as the UnrealHeaderTool.manifest file, which is located in your project directory at Intermediate\Build\Win64\Editor\[ProjectName]Development\UnrealHeaderTool.manifest, those would be very helpful.