Faulty file when using the 'faststart' option in Muxer

Hi, I get faulty file that doesn't open, when using NVENC and setting faststart to true in MP4 container in Voukoder Pro.

Sure, everything's inside. When faststart (movflags 64) is enabled in the MP4 muxer, the resulting file is unreadable. The same file processed with standalone FFmpeg (-movflags +faststart) works fine. Maybe the post-processing step to move the moov atom is failing or corrupting the file.