bug#49622: 27.2; A new MacOS display heisenbug

[Eli Zaretskii]

> From: Devon Sean McCullough <Devon2020@jovi.net>
> Date: Sun, 18 Jul 2021 09:10:11 -0400
> 
> Glyph out of place, vertically shifted downwards:
> 
> Type ;; foo ⟡ bar
> where a box ^ displays in place of the WHITE CONCAVE-SIDED DIAMOND
> which can by typed by C-x 8 RET white concave-sided diamond RET
> but renders as a box instead.
> 
> When I start Emacs, with or without init files,
> the box is rendered in the correct screen position.
> 
> After editing for a while, the box renders on the line below.
> 
>               Peace
>                       --Devon
> 
> P.S.  Please find screen shots at http://jovi.net/Emacs-Bug/Render
> 
> Any debugging suggestions?

Which font is used here?  Is it the same font in the "good" and the
"bad" display?

And why do you say this is a "new" bug? new as compared to when?

Thanks.