It is not clear to me how to reproduce this issue. When I run the demo everything is static, no flicker. OK, there is a togglebox, you probably mean that I have to click it (why don't you write that?). OK - I click the toggle box: There is a white box appearing in the combobox for a short time, approximately the size of the focus rectangle (I must press tab some time to focus the combobox and to see the focus rectangle). This happens with Laz 2.0.10, but not with 2.0.8 and not with trunk. So, probably this is your flicker, isn't it? In your sources, there is a Sleep by 200 ms, probably to exaggerate the "flicker"?
It would be easier to understand if you would write more details...
If all this is the flicker that you mean, then my answer would be: Wait for Laz version 2.2 because it seems to be fixed in the trunk version. Maybe the fix has even been back-ported to the fixes branch, but I cannot test this since I do not have a fixes installation atm.