Credit to: @ Rob Macabre for finding this solution. Make sure you thank him!
Resizable window, plug ins, and XP trackers not working?
With the launch of the Simplicity+ Client it has been an amazing addition to our gameplay experience throughout Simplicity but with something new there can be a few hiccups. I was spoiled right away with the XP trackers and all of the bonuses the client has to offer so when I ran into an issue it made me realize how helpful it is and hopefully this will fix any issues you may have for the time being as well.
Updates will be coming so don't worry but this can be an effective work around until then.
Now resizable mode can still be a bit difficult but after playing around with it I've found if you resize it one time from the top left of the window it won't freeze BUT if you play around with the size too much it can mess up forcing you to restart the client.
Thank you for your patience and keep grinding!