Builder doesn’t work since WP5.6 with and without nimble

Hallo,
Since the update to WP5.6, only a white page is loaded after clicking on “Customizer” (brush) in the admin bar. Only the heading “Your adjustments for …” and the Widgets button are still visible.
Is this a known problem?
The problem ist with and without nimble page builder.

# SITE_URL: https://www.theorie-musik.de
# HOME_URL: https://www.theorie-musik.de
# IS MULTISITE : No

# ACTIVE THEME : Customizr 4.3.14
# WP VERSION : 5.6
# PERMALINK STRUCTURE : /%year%/%monthnum%/%day%/%postname%/

# ACTIVE PLUGINS :
Add Meta Tags: 2.11.3
Ad Inserter: 2.6.18
Admin Management Xtended: 2.4.4
Akismet Anti-Spam: 4.1.7
Better Search Replace: 1.3.4
Google XML Sitemap Generator: 1.3.5
Nimble Page Builder: 2.1.28
Pre* Party Resource Hints: 1.7.3.2
Q2W3 Fixed Widget: 5.1.9
The Moneytizer: 8.0
WP-Optimize – Clean, Compress, Cache: 3.1.4

PHP Version: 7.4.13
MySQL Version: 5.5.5-10.3.27-MariaDB-1:10.3.27+maria~focal
Web Server Info: Apache