Hi, I have this ongoing issue with grid painting. You can see an example of it here:
https://www.dndcombat.com/dndcombat/Welcome.do?section=Compendium
1) Go to the page and use your scroll bar to scroll down to the bottom of the grid
2) Click on the items menu
3) Now go back and click on the Compendium menu
4) Scroll down again and this time it does not load all of the rows, at the bottom there is a blank section with rows hidden
I fix this in my production sites by reloading the grid twice, the equivalent of the table rows and you press the reload current page button which also works.
However its such a pain and creates other minor issues (e.g. performance overhead).