A grid with height:100% and auto-resize (slowly) grows indefinitely in height if the header has a non-integer height. This can happen e.g. by setting the line-height to a fractional number. See this example. The problem doesn't occur with Chrome though, but it can be seen in both Firefox and Edge.

As far as I can see the problem is cause by rounding the headerHeight down to the next integer here. Since this value is later used to calculate the total height again, the auto-resize underestimates the height of the grid and increases it slightly. The easiest fix would probably be to remove the parseInt, but I'm not sure if this could cause some new problems.