When I check some field on the grid and scroll the grid to the bottom, the checked field is unmarked, it also occurs when I do it from the bottom to the top.
Here is a JSFiddle example for reference: https://jsfiddle.net/5sxoec9z/
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We suggest saving information about checked fields to solve this case. You can see the example on the following JSFiddle: https://jsfiddle.net/flexmonster/7h6gd9Lf/3/
Please let us know if everything works fine.