visual-line-mode produces erratic behaviour with text properties

[Paul Rankin]

Enabling visual-line-mode and adding line-prefix and wrap-prefix properties to 
a long paragraph of text produces erratic navigational behaviour. Can anyone 
else reproduce?

To reproduce:

1. $ emacs -Q

2. insert a long paragraph of text
M-: (url-insert-file-contents 
"https://gist.githubusercontent.com/rnkn/d5987c3495901e4950782f6648846e4e/raw/c22074e8f0940f6ec9c8b729f04567dc50664823/loren-ipsum.txt";)

3. turn on visual line mode
M-: (visual-line-mode 1)

4. add text properties
M-: (add-text-properties (point-min) (point-max) '(line-prefix (space :align-to 
10) wrap-prefix (space :align-to 10)))

5. C-n past window length and up and around.

Expected results:

Navigation should continue by visual line.

Actual results:

Navigational behaviour becomes erratic. Point will no long move with visual 
lines, instead jumping to different columns. This is more pronounced with a 
window 80 columns or less.
 
Configuration:

GNU Emacs 24.5.1 (x86_64-apple-darwin15.5.0, NS apple-appkit-1404.47) of 
2016-06-26

OS X 10.11.4 (15E65)

MacBook Pro (Retina, 15-inch, Mid 2014)
2.2 GHz Intel Core i7
16 GB 1600 MHz DDR3
Intel Iris Pro 1536 MB

-- 
Paul W. Rankin
www.paulwrankin.com