Flyout of toolbox that has sub-categories AND sub-blocks at the same time pushes and glitches blocks in workspace #9992

Flyout of toolbox that has sub-categories AND sub-blocks at the same time pushes and glitches blocks in workspace.

I originally thought #9392 covered this, but it does not, so opening a new ticket.

The issue can also be observed in #9392, the main post video in seconds 8-9.

You can also see the problem in the video below (when I expand Math category):

As you can see, the problem does not happen with categories with only-sub categories, e.g. "Block procedures" but does happen when opening "Math" category in toolbox that has "Vectors" sub-category and some blocks at the same time.

<xml id="toolbox">
    <category name="Demo1">
        <block type="coord_x"/>
        <block type="coord_y"/>
        <block type="coord_z"/>
		<category name="Vectors">
			<block type="coord_vector"/>
		</category>
    </category>
    <category name="Demo2">
        <block type="coord_x"/>
        <block type="coord_y"/>
        <block type="coord_z"/>
    </category>
    <category name="Demo3">
		<category name="Vectors 1">
			<block type="coord_vector"/>
		</category>
		<category name="Vectors 2">
			<block type="coord_vector"/>
		</category>
    </category>
</xml>

The problem in the "demo toolbox" above will only happen with Demo1 category, Demo2 and Demo3 work fine and don't shift blocks to the side.