I think most likely is exactly which keys, mouse clicks you make. If I follow Hans steps I can enter the association and summit and have the red box displayed still.
If I click in a field and enter the data, then use the mouse to select the next field and key in the data and keep using the mouse to click in the subsequent boxes and enter the data then everything is perfect. If I use the TAB Shift-TAB key press to move between boxes then it is possible to get the red warning left behind.
If you enter partial summit details by key then select a summit from the dropdown the warning disappears. If you fully enter a summit ref by key, the warning disappears and a single summit is shown in the dropdown and if you click that summit name, the warning reappears. So don’t click the name if you have entered all the reference. Just click the next field you wish to enter.
I tested clicking in the association field and entering W6 and I waited 5+mins, no other boxes were auto-filled.