Have you checked if those files are being transcoded? This will depend on the clients used and the codecs supported. I use mine mainly to stream anime at 1080p, the files I get from my current source don’t trigger the transcoding (Direct Play); while some older files I had used unsupported codecs and required the transcoding.
Even with enterprise grade and RAID set up, some sort of backup would help.
Restic with backblaze is easy enough to set. I personally use this and an encrypted external HDD.