I filed in the newer SUnit from SourceForge.
When running the SUnit2.7 morphic UI I get a walkback in:

PluggableTextMorph(ScrollPane)>>showScrollBar
	(submorphs includes: scrollBar) ifTrue: [^self].
	self resizeScrollBar.
	self privateAddMorph: scrollBar atIndex: 1. <-----
	"scrollBar changed."
	retractableScrollBar ifFalse: [self resetExtent].

It works if I put the Preferences back to non-inboardScrollbars.
The browser, transcript, debugger don't seem to have a problem
with inboard scrollbars.

I don't have a fix; my workaround was to change the preferences
temporarily to get the SUnit UI opened with flyout scrollbars.

--yanni