I see that you use a clock to work on the "ghost" button: pay attention that whenever the clock fires, it works on the button but, if in the meanwhile, you have changed the screen, the button can be present or not, therefore the runtime error is issued.
In addition to what @Taifun has already said, please try to avoid the use of multiple screens, and allocate everything on Screen1 and look if it works. Moreover take a sight to the posts relevant to "virtual screens" (multiple horizontal and vertical layers hidden/displayed only when needed). This method avoids the use of tyniDB and also the fact that any Bluetooth communication ceases when the app changes screen.
For example here:
Best wishes for your project.