Seamless loop player for mp4 created in AFX

Hi All

Hope this isnt too 'off forum'.
I have created a seamless looped 30 second mp4 for an exhibition. It works perfectly without error in AFX and Premiere but it does not loop seamlessly in an external player which is crucial for the gallery environment it was created for. There is a tiny 'gap' in playback before it resets.
I have tried it in Quicktime Player and VLC (which didnt work at all!).

Duplicating the clip several times is not an option. The client will not go for that. The gallery has specified mp4 as the required format.

Do I need specific export settings when exporting the mp4 from AFX?
Surely there is a player out there that will do the job!! Any recommendations ?

Thanks