Thanks, Jarry!
In this case, on resizing the viewport, the first textbox inner typable area is smaller than the second one.
See the screenshot: the selected area with the red arrow shows that this area is not typable.
Screenshot:
https://snipboard.io/736zEe.jpgThe issue is even worse, if there is a button enabled on the first textbox:
https://snipboard.io/Tz5tqN.jpg