I'm having this issue constantly on macOS with .mov files (Resilio Sync 2.7.2).
I cant even use "Render and Replace" in Premiere, to render .mov files to a Resilio Sync share without it failing because of this.
It's clear that none of Resilio Sync developers read or care about these forums, so I dont expect this to be fixed soon.
I really need to find a stable alternative to Resilio Sync, because i've come to depend on it, especially during this work-from-home quarantine, but it's no longer reliable like it used to be.