@DavidSh 

It might be that the data being pushed is greater compared to the mp4 video.

Convert one of the .mov vides to mp4 and stream that to see if the video is smooth.

@Tony 

Thanks. I have tried that, and even though some of the MOV files are smaller, the MP4 videos still stream better, and none of the MOV files stream without stuttering and excessive buffering. In this case, more data doesn't necessarily lead to lower performance, as larger MP4's stream fine, small MOV files stream poorly. Perhaps there is something inherent in the MOV file type that causes problems?

I have hundreds of MOV videos (and more being made all the time on iPhone), so converting them all needs to be avoided if possible. I want to figure out why that specific format won't stream, even with VLC or other "universal" media players. I'm willing to make additional hardware or software investments if I can find a solution.

I suspect something in the router configuration or router hardware deficiency. I should add that I have tried both 2.4 and 5 ghz bands on multiple router channels, and performance is equally poor with MOV vido files.

Why is so much online file converter but they are too slow? what other services can you offer on an example like this here?