_wp_page_template is getting 'stuck' to a page

[shawmutsteve]

Unmodified WP 3.4.1 / Ummodified TwentyEleven theme

Create a page (id=2). Manually add a postmeta entry for

post_id=2, 
meta_key = _wp_page_template, 
meta_value = pagefull.php

The page now opens with margin: 0 7.6%; (correct!)

Now try to change it back to default, either by removing the _wp_page_template postmeta record or by editing the page -> Page Attribute / Template. The page will not revert back to Default. It continually displays as Full Width, and a postmeta item telling post_id 2 to use _wp_page_template = pagefull.php is added.

​http://wp34.roveridx.com/?page_id=2

This behavior does not happen in 3.3.2.