The cause of the issue is brought about by how you switch screens.
Looking at the Screen 'Form', 'Open another Screen' is used to open Screen 'Menu'.
However, in Screen Menu there is 'Open another Screen' to open Screen 'Form'.
What that is doing is literally opening another Screen 'Form', so now there are two of them in allocated memory and the latest, empty one you just opened is the one displayed. That accumulation in memory will eventually make the App crash.
If instead you do this:
The User will be taken back to the Screen that launched the current Screen, i.e. Screen 'Menu'.
It's a pity we didn't hear from you earlier because we would have recommended using Virtual Screens instead - they are all in the same memory allocation and so the data is retained:
When we define virtual screens, we use one 'real' App Inventor Screen (most often Screen1). Screen-sized Vertical Arrangements on it are displayed/hidden as required - they are the Virtual Screens. This is generally a better approach for multi-screen Apps, they share data without having to "pass" it between screens and it also reduces code duplication, making the App more efficient and the code easier to follow if you have to return to it at a later date.
So, instead of separate "houses", virtual screens are "rooms" of the same "house".