I don't understand what you're saying. I don't think the specific arena matters, nor the density of the clouds, or frame rate, or radar settings.
There is an inconsistency: The icon of enemies concealed by clouds vanishes, but the selection box remains visible. That's simply inconsistent. Either the icon should remain visible in clouds, too, or the selection box vanish like the icon. However, it seems intentional that the icon vanishes (else it wouldn't) - and the target selection box was simply forgotten (maybe not so easy, as F11 mode would need to stop following too at that moment).