Seems like it still closes the file out after 9 seconds, which is strange.
egrep 'ONLY|Flush' log.log | grep Sky
2019/04/01 20:44:28 DEBUG : My Drive/Downloads/Movies/Skyscraper (2018)/Skyscraper.2018.1080p.BluRay.REMUX.AVC.Atmos-EPSiLON-Obfuscated.mkv: Open: flags=O_RDONLY
2019/04/01 20:44:28 DEBUG : &{My Drive/Downloads/Movies/Skyscraper (2018)/Skyscraper.2018.1080p.BluRay.REMUX.AVC.Atmos-EPSiLON-Obfuscated.mkv (r)}: Flush:
2019/04/01 20:44:28 DEBUG : &{My Drive/Downloads/Movies/Skyscraper (2018)/Skyscraper.2018.1080p.BluRay.REMUX.AVC.Atmos-EPSiLON-Obfuscated.mkv (r)}: >Flush: err=<nil>
2019/04/01 20:44:29 DEBUG : My Drive/Downloads/Movies/Skyscraper (2018)/Skyscraper.2018.1080p.BluRay.REMUX.AVC.Atmos-EPSiLON-Obfuscated.mkv: Open: flags=O_RDONLY
2019/04/01 20:44:29 DEBUG : &{My Drive/Downloads/Movies/Skyscraper (2018)/Skyscraper.2018.1080p.BluRay.REMUX.AVC.Atmos-EPSiLON-Obfuscated.mkv (r)}: Flush:
2019/04/01 20:44:29 DEBUG : &{My Drive/Downloads/Movies/Skyscraper (2018)/Skyscraper.2018.1080p.BluRay.REMUX.AVC.Atmos-EPSiLON-Obfuscated.mkv (r)}: >Flush: err=<nil>
2019/04/01 20:44:29 DEBUG : My Drive/Downloads/Movies/Skyscraper (2018)/Skyscraper.2018.1080p.BluRay.REMUX.AVC.Atmos-EPSiLON-Obfuscated.mkv: Open: flags=O_RDONLY
2019/04/01 20:53:06 DEBUG : &{My Drive/Downloads/Movies/Skyscraper (2018)/Skyscraper.2018.1080p.BluRay.REMUX.AVC.Atmos-EPSiLON-Obfuscated.mkv (r)}: Flush:
2019/04/01 20:53:06 DEBUG : &{My Drive/Downloads/Movies/Skyscraper (2018)/Skyscraper.2018.1080p.BluRay.REMUX.AVC.Atmos-EPSiLON-Obfuscated.mkv (r)}: >Flush: err=<nil>
I think your issue relates back to another post with a deadlocking item and something expiring from your directory cache.
Can you try to update your --dir-cache-time to something higher?
VFS Mount Freezes was the item I was thinking of when I read this as it’s only when you are writing the file and probably when it expires the cache perhaps.