bug#39564:

[Matt Kramer <mccleetus@gmail.com>]

Code I used:

(defun make-lines (n)
  (mapconcat #'number-to-string
             (number-sequence 0 n) "\n"))

(let ((map (make-sparse-keymap)))
  (define-key map (kbd "C-f") (lambda ()
                                (interactive)
                                (let ((inhibit-field-text-motion t))
                                  (goto-char (point-min)))
                                (message "%S"
                                         (read-key
                                          (concat
                                           (make-lines 10)
                                           "\nTest2")))
                                (abort-recursive-edit)))
  (read-from-minibuffer (concat (make-lines 10) "\nTest1: ") nil map))

With this code in the clipboard, I start emacs -Q (again, 27.0.60
commit 75a9eee8b), and immediately hit the following sequence of keys:

C-y
M-x eval-buffer RET
C-f

The eval-buffer results are initially as expected. However, after
hitting C-f, the minibuffer then becomes:

0
1
2
3
4
5
6
7
8
9
10
Test1:  [0
1
2
3
4

with point at the very beginning of the minibuffer (first 0).