Strange window behavior

[Bob L]

MacPro4,1 Nehalem upgraded to 5,1.
2x 6 core 3.33 GHz, 24 GB RAM.
GT120 stock video, 2 displays.
850 EVO 500 GB, 2 partitions.
Money partition is PT 12.4 Vanilla, OS X 10.8.5.
New partition is PT 12.7.0 Vanilla, macOS Sierra 10.12.3.

On the 10.8.5 (Money) partition, plug in windows behave normally. Put 'em on any display over Edit or Mix windows, they appear normal.

On the 10.12.3 (New) partition, opening a plug in either window on either display is normal. See "EQ3 Main Window".

Moving the same plug in to the opposite window and display results in a white replacement of the header controls. See "EQ3 Second Window".

It doesn't matter which display is the "opening" one, the "moved" one shows the white header. 100% reproducible.

This happens with Avid plugs (EQ3, Fairchild 670), Izotope (Ozone 5, Ozone 7 Advanced, Insight), Plug In Alliance (bx_meter).

I have downloaded, but not installed 12.7.1.
I do not have Sierra 10.12.2 available.

I seem to recall a similar thread from several months ago, but I can't find it, so here I am clogging the internet for a solution.

[cwsand]

Hi, My first guess would be a video driver issue. Have you checked to see if there's an update available? (Make sure you have a backup ready in case it causes problems!)

[Bob L]

Originally Posted by cwsand

Hi, My first guess would be a video driver issue. Have you checked to see if there's an update available? (Make sure you have a backup ready in case it causes problems!)

Thanks, Chris. The GT 120 doesn't appear to have any updates, unsurprisingly given its age.

Further troubleshooting...
Deleted Prefs... No difference
Installed 12.7.1... No difference

Further observation...
Once moved to the opposing display, the borders and controls go white as before. Closing the plugin from the Insert display in either Edit or Mix window and reopening heals the window and leaves the plug window in the last place it was dropped.

Kind of a workaround.

[Bob L]

Thanks to some work by Macsearcher, a working workaround works.

Thank you Macsearcher!