C# disappear buttons

i have an application created by Bunifu UI framework. after run it and working on it for a while when i hover my mouse on buttons or objects on the form suddenly disappear buttons and all objects that i hover on it in the form, But i can click on the buttons But when i click on it gives me this error on Designer of the form says: Out of memory or sometime says: Operation completed or says: Invalid handled.

please help me to solve this problem thank you..