If you have a global variable and a sub of the same name and reference the variable in the sub then Dbasic crashes without emitting a warning.
This had me panicking for a while - the code that started doing it to me was not quite as straightforward as the fragment above that I distilled the problem down to.
B4X:
Sub Globals
'Declare the global variables here.
fred = true
End Sub
Sub App_Start
Form1.Show
End Sub
Sub fred
fred = true
End Sub