Browser cache control for mp4 doesn’t work

I purchased Smart Slider3 Pro.

Make an mp4 slide in the slide, set the URL, and the movie will flow well.

However, a large communication band is required because the movie is downloaded every time.

I want to use the browser cache to reduce the required communication bandwidth.

.htaccess
<ifmodule mod_expires.c=””>
ExpiresByType video/mp4 “access plus 1 month”

Set Expires in server .htaccess, and in the browser header,

Cache-Control: max-age = 2592000, public

I confirmed that it was displayed.
However, when the slides are in mp4 order, mp4 data will be downloaded every time.
By the same method, jpeg uses browser cache and communication does not occur.
I want to use a browser cache, what should I do?