cannot play media in one click, i need to keep retrying so the media can play

[Idnawsi]

so, when i tried to play a media on my server through WAN, it will just stuck there loading, when i check log, i got the slow http response, and after that, i got ffmpeg exited 0, and no matter how long i wait, it will never play, it just show the 1 frame of the video and just circling buffer animation, i need to refresh, and retry everytime but once it play, any video will just play in one click, what could be the problem?. but playing local is fine, i already set my mss low enough so there is no mss mismatch and checked it with wireshark.