Rederict issue

Hello,

I can’t redirect to a page anymore in this plugin.
In the backoffice, if I want to set te reirect page, I get the following message: “A variable mismatch has been detected”. I’ve tried to set a different page, but I get the same result.

Version of WordPress = 4.9.9, which (according to the official plugin page) should have been tested. The plugin is up-to-date.

Don’t hesitate to ask for more info if it could help solve this issue.

The page I need help with: [log in to see the link]