I have a web app viewer app that has a copy of the BLM Township layer, where pop-ups are working consistently.
I am recreating the same app in Instant apps. The pop-up window for townships doesn't consistently open when I click in the middle of a township.
I have found that when I scroll in close and click on the outside line of a township then it will generally open the pop up window but not always.
Here is a video of clicking on the pop up window in the web app builder app to show that it is working consistently:
Here is a video of clicking on the same pop up window in the instant app: