[2.0b1][CLOSED][was not a bug] Firefox FormPanel colapse and scroll bug
I think there is a bug on collapsible and scrollable formpanels.
when first panel collapses & expands second one goes out of it's borders also there is an unwanted behavior on this panels on collapse and expand in firefox.
I don't think there is a bug here. I've reproduced your problem locally but there may be some conflicting configuration options.
The problem is because you have a static height of 400px and your content overflows the container. You need to set an appropriate layout such as accordion, set autoScroll: true, or make sure the height of the container will support all of the items you are going to put in it.