This is possibly an issue with your theme css or other css being added to your site. Something is possibly forcing it to float to left, or preventing it from being treated as inline-block element.
There are also various important CSS parse errors at your site. These can easily break the rendering of the elements at any point.
https://validator.w3.org/nu/?doc=http%3A%2F%2Fsasquatters.com%2Fwhats-going-on%2F
It’s just weird to me that this is the only thing on the site not working properly. And even half of the centering is working (the text part). We are on the latest WP version so maybe that has something to do with it.
Nope, its not weird at all – when HTML or CSS is broken via a theme or plugin (or custom code) it would pop up wherever the interpretation of html or css flops. This could have been anything – possibly there are more things broken at the site, but not visible due to being same color with bg or not appearing etc.
A broken HTML or CSS code is something that needs to be debugged directly. Enabling/disabling the plugins and checking validator to see which plugin breaks it, and also testing with other themes to see whether it is the theme are good ideas.
Latest WP version cannot have anything to do with it.
I disabled every plugin but yours and the button is still showing in the wrong place.
Did you change your theme and see if theme is effecting it?