steps to reproduce

run the example and click the buttons in sequence:
A, B
B, A
A, B, C, D
A, B, C, D, E, A

actual result

When autoscroll is enabled, the content is overlapped by the scrollbars
When autoscroll gets disabled the content does not occupy the available area (of the removed scrollbar)

After resizing the browser window or calling Clients.resize(mycenter) (C) the container fits as expected

expected result

the container and content sized by hflex should autofit into the available area

Workaround

calling Clients.resize(mycenter) after changing the autoscroll property