Index: wp-admin/admin.php
IDEA additional info:
Subsystem: com.intellij.openapi.diff.impl.patch.CharsetEP
<+>UTF-8
===================================================================
--- wp-admin/admin.php	(date 1586617751000)
+++ wp-admin/admin.php	(date 1586637419960)
@@ -35,7 +35,7 @@
 
 nocache_headers();
 
-if ( get_option( 'db_upgraded' ) ) {
+if ( ! wp_doing_ajax() && get_option( 'db_upgraded' ) ) {
 	flush_rewrite_rules();
 	update_option( 'db_upgraded', false );
 
@@ -45,7 +45,7 @@
 	 * @since 2.8.0
 	 */
 	do_action( 'after_db_upgrade' );
-} elseif ( get_option( 'db_version' ) != $wp_db_version && empty( $_POST ) ) {
+} elseif ( ! wp_doing_ajax() && get_option( 'db_version' ) != $wp_db_version && empty( $_POST ) ) {
 	if ( ! is_multisite() ) {
 		wp_redirect( admin_url( 'upgrade.php?_wp_http_referer=' . urlencode( wp_unslash( $_SERVER['REQUEST_URI'] ) ) ) );
 		exit;