For those who are still having some issues with Objects shown through Clouds/Fog in P3D V5.1 (even with the latest HF) there is a work around.
LM provided some information on his forum (Lead Beau Hollis) after I reported having some issues with the EA mode.
NOTE: There is a side effect......please read that thread at LM Support carefully.
LM admitted to have this issue, based on my report (z-bias related and it´s values do cause this). Although lots of 3th party devs are stating everything should and is solved with HF1, it is NOT at the moment.
Links you will find below.
In my case and opinion, I can life with that side effect and so I use the work around.
Link LM Support with reported issue and temp work around:
https://www.prepar3d.com/forum/viewtopic.php?f=6312&t=141012#p234396
Link Related BUG coming with P3D V5.1 (incl HF1) and wrong rendered 3dmodels viewed at at further distances due z-bias changes:
https://www.prepar3d.com/forum/viewtopic.php?f=6312&t=136958
Happy landings incl. nice views!
Marcus