Disable conflicting plugins on UM pages.

um_conflicts_fix.php

<?php
/**
 * Plugin Name: Ultimate Member - Conflicts Fix
 * Description: Disable conflicting plugins on UM pages.
 * Author:      Ultimate Member support team
 * Author URI:  https://ultimatemember.com/support/
 * Version:     1.0.0
 *
 * Add this code to the file /wp-content/mu-plugins/um_conflicts_fix.php
 */
if ( ! function_exists( 'um_conflicts_fix' ) ) {

	function um_conflicts_fix( $active_plugins ) {
		if ( is_admin() || wp_doing_ajax() ) {
			return $active_plugins;
		}

		// List of Ultimate Member pages.
		$pages = array(
			'account',
			'login',
			'members',
			'password-reset',
			'register',
			'user',
		);

		// List of plugins that conflict with Ultimate Member.
		$plugins = array(
			'forminator/forminator.php',
			'supportcandy/supportcandy.php',
		);

		if ( ! empty( $_SERVER['REQUEST_URI'] ) ) {
			$uri = trim( wp_unslash( $_SERVER['REQUEST_URI'] ), " \t\n\r\0\x0B/\\" );
			if ( strpos( $uri, '?' ) ) {
				$uri = trim( current( explode( '?', $uri ) ) );
			}
			if ( strpos( $uri, '/' ) ) {
				$uri = trim( current( explode( '/', $uri ) ) );
			}
			if ( in_array( $uri, $pages, true ) ) {
				$active_plugins = array_diff( $active_plugins, $plugins );
			}
		}
		return $active_plugins;
	}

	add_filter( 'option_active_plugins', 'um_conflicts_fix', 10 );
}

Most of the time when you find an issue on your site with Ultimate Member, it will be caused by a plugin or theme conflict. Follow steps in the article How to do a plugin/theme conflict test? to find plugins that conflict with Ultimate Member. Contact the plugin support to ask them solve a conflict.

As a temporary solution you can disable conflicting plugins on Ultimate Member pages. Use mu-plugin to do this.
Create the /wp-content/mu-plugins/um_conflicts_fix.php file and paste this code into the file.

Go to wp-admin > Plugins > Must-Use. You should see the "Ultimate Member - Conflicts Fix" plugin. This mu-plugin disables plugins listed in the $plugins array at pages listed in the $pages array. You can extend these arrays if you need to disable other plugins or do it on other pages.