What is this error is about?

[Vaibhav]

You are either using some heavy images or you are not switching screens properly or else may be both

See tip 1 & 2 here

General Tips and Tricks for App Inventor/Kodular

Use different screens wisely Before starting to create another screen, first you should think about is it really necessary? See also Building apps with many screens and SteveJG’s post about advantages/disadvantages, because in only one screen you also can use vertical arrangements to simulate different screens, just set the arrangements to visible = true/false as needed… If you decided to use different screens, then you should switch them correctly, else you will run out of memory after a wh…