When nesting SplitPanes (e.g. a horizontal SplitPane with 2 items where the first item is a vertical SplitPane with also 2 items.) then under some conditions the horizontal divider of the root SplitPane shows up all to the left (value around 0, e.g. a debugger session showed 0.0020026702269692926) and the content of the second item is not shown, just the background of the SplitPane (I changed the background color to verify this).

When I manually increase the window width after start-up everything is rendered as expected. Changing the height or decreasing the width has no effect, but manually changing the divider works as well.

There are different seemingly unrelated conditions which cause the same effect and I haven't found workarounds for all of them yet.

I will try and provide some SSCCEs which show the issues.