Vertical Scrolling Arrangement, Internal Error Occurs

In the app layout I wish to use one Vertical Arrangement (VA) and two Vertical Scrolling Arrangements (VSA). The intention is that the two VSAs will be switched to visible / not visible as necessary.
The VA has three Horizontal Arrangements each with with buttons and labels etc. One VSA has nine Horizontal Arrangements each with buttons etc. So far so good. However as soon as I add in the second VSA I get an 'Internal Error' bug reported. Even after I delete the second VSA the bug report persists. I've had to resave the app with a new name to get out of a perpetual error loop. Does anyone know what's going on? Are apps limited to one VSA??

I am not able to emulate your issue. (I added the two VSAs to the VA first, then added HAs etc.)

If you can create an aia project that reproduces the issue, I am sure MIT will take a look.

Thanks, that's interesting. Maybe it is my code that is raising the error. The moment I go into 'Blocks' the error notice comes up and the whole screen locks up, so no way of editing the code if indeed that is the problem. As the error was raised after 'Design' layout changes I assumed that was the source of the difficulty. It is a multi-screen app and it is only the one screen that is misbehaving...