essential mistake

hi.
you have this (on 230 line) in your plugin:

if ( strpos($userrequest, '/wp-login') !== 0 && strpos($userrequest, '/wp-admin') !== 0 )

and instead of strpos, its better to use stripos,
because someone might use /WP-LoGiN or etc..

https://ww.wp.xz.cn/plugins/simple-301-redirects/