Slide In has errors upon activation

The following error messages appear at the top of my page when Slide in is activated:

Strict Standards: Redefining already defined constructor for class Wdsi_Options in /home/agileaqu/public_html/wp-content/plugins/slide-in/lib/class_wdsi_options.php on line 9

Warning: Cannot modify header information - headers already sent by (output started at /home/agileaqu/public_html/wp-content/plugins/slide-in/lib/class_wdsi_options.php:9) in /home/agileaqu/public_html/wp-content/plugins/sg-cachepress/class-sg-cachepress.php on line 251

Warning: Cannot modify header information - headers already sent by (output started at /home/agileaqu/public_html/wp-content/plugins/slide-in/lib/class_wdsi_options.php:9) in /home/agileaqu/public_html/wp-includes/pluggable.php on line 1196

I've tried deleting and reinstalling the plugin as well as clearing SG cache and WP Rocket cache.