Attached screenshot shows the top of the scrim highlighted with a yellow oval. Below the scrim, the map was unresponsive; had to drag it down via the top line to regain touch access to the map. White/blue add button slid down with top of scrim.
Couldn't reproduce it. Best that I can tell is that I was trying to clear the last-entered point display so that I could enter a second point. Lots of poking and dragging of bottom window.
Collector 188.8.131.5266, iOS 13.1.2, iPhone XR