Middle Mouse drag Issue in Heroes of the Storm

[darkstego]

While using synergy I get an issue with drag scrolling (scrolling while holding middle mouse button) while in the game Heroes of the storm. It starts scrolling fine, but after a short while it start dragging with a clear delay and then proceeds to bounce all over the place everytime I hold the middle mouse button. This issue was not in 1.7.3, but it does occur in 1.7.6 and the 1.8 beta. This is under Win10 64bit.