I tested your demo with Laz 1.6.4, 1.8RC5, and Laz-trunk and can confirm the behavior for 1.6.4 and 1.8RC5 on Win10. Laz-trunk, on the other hand, does not show the issue. I think I remember I once saw such a bugreport, but I cannot find it at the moment. Obviously this fix has not been backported to 1.8RC5, I don't see it in the list of fixes waiting for RC6 or final either.