master slider text breakdown on Firefox

Hi there!

I’ve got some problem with text breaking up on Firefox using Masterslider.
other browsers works fine except Firefox.
my site link is http://www.opticleanau.com and the Masterslider content is located at the home page where the full-width video background is playing.

Please help me to fix this problem.

Thank you.

https://wordpress.org/plugins/master-slider/