Sound Level to Plugin is wrong

Further to my previous post, it seems I’m not the only one.
Someone else having what sounds like exactly the same problem but using another loudness measuring plugin:

He was using an earlier version of Audacity, but it seems the problem remains in later versions.

The conclusion thus far, is that there seems to be no fix to this (judging by no replies from the other post).
Pity, as Audacity is a really easy piece of software to use and get to know, but cannot be used for any serious leveling work.