If you resize the client while on the oldschool preset, objects will 'flicker' until the ends of time, across resets and everything. The only solution is to go into a different preset layout and stay there. If you switch to legacy mode from the flickering oldschool you will get the flickering anyways. You need to choose a different preset and then switch to legacy mode to avoid the flicker. Edit: I can confirm that no flickering occurs on any of the other presets regardless if you resize the client.
