First, please do send the crashing script to Tech Support - even when the script is not doing things the recommended way, we would like to fix any mishandling that leads to a crash.
Stretchable displays have many considerations - it would be helpful to know how you are creating the stretchable content. Platforms like Graph Builder have built-in settings like Fit To Window("On"), while for custom content you may be using something like frameBox<<Set Auto Stretching(1,1). If you have an example that you can attach, that would be ideal.
Even when content is stretchable, the window will still measure all of the boxes and size the window large enough to contain everything (if possible, otherwise it may have to scroll). When adding stretchable content you may want to set the initial size to something small if you don't want the new object to cause a change in the window size. You may also find it useful to call <<Set Min Size() or <<Set Max Size() on the stretchable content - this can change the behavior of stretching when the window is made larger or smaller.
Another thing that you may want to look into is the use of Splitter Box. Splitter Box can help to keep stretching in sync between multiple stretchable objects, and lets you define the initial size of the content. This is counter to the comment above about the window growing large enough to contain the content - Splitter is more forceful about maintaining a size and forcing the child boxes to adjust.
Names Default To Here(1);
dt=Open("$SAMPLE_DATA/Big Class.jmp");
New Window( "stretch",
H Splitter Box(Size(900,600),
<<Sizes({.3,.7}),
V Splitter Box(
dt<<Bivariate(
Y( :weight ),
X( :height ),
SendToReport( Dispatch( {}, "Bivar Plot", FrameBox, {Frame Size( 201, 170 ), Set Auto Stretching( 1, 1 ), Set Min Size( 50, 50 )} ) )
),
dt<<Oneway(
Y( :height ),
X( :sex ),
SendToReport(
Dispatch( {}, "Oneway Plot", FrameBox, {Frame Size( 214, 172 ), Set Auto Stretching( 1, 1 ), Set Min Size( 50, 50 )} )
)
)
),
dt<<Graph Builder(
Show Control Panel( 0 ),
Fit To Window("On"),
Variables( X( :height ), Y( :weight ), Overlay( :sex ) ),
Elements( Points( X, Y, Legend( 1 ) ), Smoother( X, Y, Legend( 2 ) ) )
)
)
);