Look at all the posts about upgrading to V4 and you will see lots of spurious files issues resulting from not backing up and reformatting. I can't say doing this will fix the problem because I don't recall anyone with this problem before.
He is streaming from a nas and not from a disk inside a mede8er.
My guess is that this is a compatibility issue with HDMI EDID as discussed before in this topic.
So yes, only downgrading to prev firmware will help, a version 3