I use Agama Pro with three Agama slides on the frontpage. I changed the button text for the slides in the customizer and the text is accepted as long as I am in the customizer view.
When I switch to normal page preview (without customizer) the text is the default text “LEARN MORE”.
The problem can be caused by the conflict with some of the plugins you have activated, so I suggest you check the plugins first.
To do that, deactivate ALL plugins temporarily to see if this resolves the problem.
If this works, re-activate them individually (one-by-one) to find the problematic plugin(s).
So please, check that first, and then if the problem still persists, please let me know.