Again, I can't reproduce that behaviour. The only way to get this issue would be to use deprecated landmarks (landmarks created before the level of the floor was raised (i.e. floor prims added or raised), for example, but then the "half avatar height offset" is in no way a solution, since the amount of meters the floor is raised is unknown and could be anything).
Official viewers don't have it, and if something like that was truly happening with current, valid landmarks, I'm pretty sure there would have been a fix in those viewers already.
If you can reproduce the issue with a landmark you just created, please send me that LM for testing.