NAS skipping frames on movies

Hi everyone!

I have a weird one that has been bugging me for quite some time.

On my DS220+ (with 2 Seagate IronWolf Pro 12Tb), I am having issue with frame skipping on some movie files.

The file would work absolutely fine on my laptop (checking it with VLC), but once copying it (either via Wifi or Ethernet) on my NAS, then it ALWAYS skips frames at the exact same timeframe (to the point where VLC just close the file by itself without continuing playing the movie).

On infuse, the file/and sound will keep going, but the image will stop for a few second and jump to a new timeframe on the movie. On some files, it happens every 5min, so not fun :) .

The NAS was plugged onto a unmanaged switch. I tried by plugging the NAS (with a different wthernet cable) directly to the Synology router. No luck, same results.

It's driving me nuts. The main reason I bought that NAS was to use infuse to play movie on my Apple TV, and it just doesn't work!