Gamma Tag Bug MOV washed-out


I am experiencing the Gamma shift Bug (Metadata Tag) when converting MOV Quick Time files into MP4 h264 with any normal video converter software. The output file looks washed-out.

When converting those MOV files with ffmpeg the output looks as the original file. But the Gamma Tag is still inside the MP4 files, which makes it impossible to further edit the files.

How can I erase or rewrite the Metadata to come across of the Gamma Shift Bug?

(Only when converting the files with the Wondershare Converter the output files look like the original and the Gamma Tag is erased from the Metadata inside the output file.
Can you tell me what is different about the Wondershare Converter and why it manages to erase and rewrite the metadata?)