Plugin Window Disappears if I select another Track

[Markrosoft]

Either updating to 2019.5 or deleting my preferences is causing something I've never experienced: if I open a plugin window and then just select a different track (NOT another plug-in, but literally just select another TRACK) the plugin window I opened disappears.

So, just to make this clear... I open Kontakt on a track called Piano. Then I just click on a track called cello and my Kontakt piano disappears.

This never used to happen and for the life of me can't find where the setting is to change this back to the normal behavior - a plugin window stays open until you close it or open another plugin. I know I can click the red box to leave the plugin open but again, I'm looking to return it to the default behavior.

Does anyone know where this preference can be changed?? Thank you for your help!!