Acer T232 Touchscreen and MacOs Sierra

On a late 2012 27" iMac and Acer T232HL monitor connected via thunderbolt to HDMI:

Prior to the Sierra update I just installed, I had touchscreen capabilities working acceptably well on this external monitor for the simple tasks I need to perform (mostly touching onscreen buttons). I just upgraded to Sierra and am having a major issue: whenever I touch the screen, several buttons are selected, as if a was holding down "shift" and selecting an area.

I tried rebooting, and searching for any sort of setup tools on the monitor or the Mac, but with no luck.

Anyone having similar issues? Is there a way to adjust/calibrate? Or do I need to report a bug?

Thanks,

Brad