You could try this javascript in the page header. It should complete before the page is fully loaded:
$(document).ready(function() {
document.title = "New Page Title";
});
If that works you can figure out the best method to load the dynamic page title from Bubble/API/External DB. I have no idea if this will solve your SEO problem. I wouldn’t think having Bubble “cache” your page title data would be a big deal, but I don’t know your data structure.