Choosing Customizer gives HTTP500 error

Dear support, I have Catch Responsive Pro 4.2.3, WP 4.9.5, I use Firefox and Chrome, both with Privacy Badger and HTTPS Everywhere. Windows 10 Home 1709. The customizer for the theme gives a HTTP500 error. I tried to disable Privacy Badger and HTTPS Everywhere, this did not change the error. I have enough memory on the server. Please advise. Thanks in advance. Regards Alexander