ARP_ASUSI did as told with the SMMI test and it concluded no issues with the touch screen, and to answer the first question, no i havent factory reset the phone after updating to a12 as ive noticed no other issues other than this
Have you tried Factory reset after the new update? Are you using any scratch guard?
Please follow SMMI test and check if there is any abnormalities:
How to Enter SMMI_TEST (test hardware)
Go to Calculator=>type " .12345+= "
you will be entered to SMMI_TEST