>> By the way, using Ihor's suggestion, I was able to debug the issue.
>> There is nothing wrong with my configuration. The issue is that the
>> font cannot deal with that symbol, and LaTeX just skips it. Still, it
>> would be convenient not to have to create a separate .tex to debug
>> the preview. Thanks!
>
> AFAIR, the new preview system will record possible issues with previews
> and mark them appropriately in a tooltip.

In this specific case, it was recognized as an error.  Here is an image
of the result and the tooltip message with the new LaTeX preview system.

I typed \(μp + 1\) because getting a screenshot of the tooltip with just
the rendered `p' was tricky.

Karthik