Trouble playing video over network shares

Ever since upgrading to 10.13.2 I'm having issues watching any videos stored on my NAS and PC.

It seems my Macbook pro downloads the whole video file first before starting playback (confirmed using network monitor).

I've tried this:

- Reinstalled high sierra through app store

- Created a new local user

- Disabled gatekeeper

- Mounted using AFP, SMB, CIFS

- Tried various video players (VLC, Movist, Quicktime)

- Changing permissions of the files on the NAS (removing the executable flag)

Nothing seems to work.. It happens with both my NAS as well as my shared PC folders.

Don't have any issues when trying to play the files using my PC, Ipad or any other gadget.

It's driving me crazy! Anyone has any ideas?