Getting Error The link you followed has expired.

I have a similar problem. I already have 499 redirects and when I try to add number 500 I get an error saying “the link you followed has expired”. Other then that the plugin has always worked fine. I have raised all PHP values such as time out to the max but still it does not add the next redirect. I don’t know, its funny it happens with redirect 500. Are there any limits to this plugin or any solutions available please? I can open a separate ticket if you so prefer. Many thanks in advance.