when rendering grid rows deferred they might change in height and then fail to initialize a scrollbar column (see attached example the 2 cases on the left)
the 3rd case shows a workaround by applying a height to the z-renderdefer dummy rows to cause a scrollbar initially.
(however this only works reliably if the height is known in advance)

the 4th grid shows what it should be like when not using "renderdefer"