Steps to reproduce:

1. Open any PDF document in the Acrobat Reader DC on Windows (my version 2021.001.20138)

2. Change the following (I do it for every single document, that should be the default):
   View -> Page Display -> Single Page View
   View -> Zoom -> Zoom to Page Level
   View -> Read Mode
   View -> Show/Hide -> Menu Bar

3. Resize the window so that the page takes up precisely 100% of the window area, there are no blank margins around the page.

4. Close the window

5. Open the same document again

Expected behaviour:
Window size should be remembered. When you apply all the actions from step 2, the page will fill up precisely 100% of the window space.

Actual behaviour:
Window height will be slightly larger. When you apply all the actions from step 2, some narrow blank area appears below and above the page. Each time you do that, window height grows bigger and bigger. After opening the document several times (each time hiding the menu bar) the window becomes taller than the screen!