I run Emacs 26.1 with a config of just:

(setq scroll-error-top-bottom t)
(setq scroll-preserve-screen-position 'always)

I open a long file, hit PageDown, then the Down key a few times. Point is
at some position X now. I come back to the beginning of buffer by hitting
PageUp twice. The point is now in the top left corner of the window. Here
comes the bug: I hit PageDown and point is moved to position X, rather than
to the top left corner of the portion of the buffer that was just made
visible by the scrolling. The scrolling itself seems to work OK.

Cheers,
Jarosław Rzeszótko