white screen with version 4.2

Hallo,
after updating register plus redux to version 4.2, we have a blank screen at the Backend of our wordpress. The Frontend still works normally.
I have deactivated all other plugins with no effort. Even a change of the Themes doesn’t helped.

Register-plus-redux is a great plugin, and we want to use it in Future too. thx for your help
regards
Eddie

https://ww.wp.xz.cn/plugins/register-plus-redux/