In preview mode of a question, after "testing", there is the need to repeat the test with the same random parameter values as before. - This is essential when debugging a complex question because the need arises to examine how the logic responds to varying combinations of correct and incorrect responses in the answer boxes.
There is a substantial jitter issue which seems to have its roots in, the system not being able to make up its mind about whether it needs a vertical scroll bar on the right. - Scroll bar visible/not visible causes very troublesome jitter. If I shorten the height of the browser window so that a vertical scroll bar is always needed, then the system still jitters, this time seemingly with a second vertical scroll bar inside the original one.
Issues in the Preview UI