If you are unable to open Oxygen Builder page/template, which load forever, go to Oxygen > Export & Import page and confirm that the Export JSON isn't loading. Then you can use the below Snippet as instructed below.

This code is to fix the most common cause of Oxygen getting stuck on tweaking typography or large amounts of parse errors.

To use this snippet, install a snippets plugin that allows you to run a snippet one time, such as Code Snippets or WP Code Box (paid). Then, add this code and run it once.

<?php
if(!function_exists('oxys_restore_presets')) {
	function oxys_restore_presets() {

		$presets_option = get_option('oxygen_vsb_element_presets');

		if (($presets_option)) {

			delete_option( 'oxygen_vsb_element_presets');

		}

	}
}

oxys_restore_presets();
?>