I was provided a link by ZWO Seestar tech support (using the bug report feature in the app) that let me install V2.2.0 Build 2.
This Build 2 of the latest app fixed the problem and my tablet (Samsung Galaxy Tab A with 3gb RAM) is working well again. I am able to see the preview images as they are taken.
Build 2 did not change the firmware on the Seestar device, so the issue, whatever it was, was fixed by a change in app software only.