HLG files not always output as HLG

Hi,

I have a strange oddity when processing HLG files on Final Cut Pro X. I have an Osmo Pocket 3, I record in HLG, when the memory card is plugged into the TV all the files show as HLG. When I process the files as wide colour HLG and export them as HLG, the exported file does not always show as being HLG even though the settings have not changed, the TV does display Dolby Vision but not that the file is in HLG. Again, this does not happen for all the files created in HLG, the majority display as HLG. It is not a great problem, the files look great but just cannot work out why they are being handled differently. Any thoughts?