Header flickering and freezing issue with material table (implemented with react window + react window infinite loader)

I have implemented an Infinite scrolling table with react-window (based on #60) and material UI.

The table seems to be fulfilling the main objective but there are few issues with it -

1. header is not sticking on the top in spite of having styles in place (stickyHeader prop).
2. header is flashing/flickering while scrolling quickly towards up direction. [Steps to reproduce - scroll 50% down then do fast scroll up and observe the header movement ].

Here's the codesandbox example - https://codesandbox.io/s/react-window-with-table-elements-forked-huti6?file=/src/index.tsx:514-542

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