Problem with last row rendering, hover over active tab triggers scroll shift

[bgui]

Seems when there are rows scrollbars the last row does not get shown entirely. It's like the scroller does not go to bottom, but instead scrolls up a few pixels (from the bottom) but only when I hover over current active tab then all rows get shifted up and last row is fully in view. Hover over Inactive tabs don't trigger the shift.
Is there some border or something that I could add/reduce to fix this? This is on win7.

the flickering and shifting are annoying. Thanks for all the hard work !

[bgui]

Hmm it seems that if I disable "new tab" button then lift goes all the way down and problem goes away.