Steps to reproduce:

1. Prepare a test eZ Publish 5.4 installation, fully updated;
2. Create a new class that contains an attribute of type "checkbox" (see "5023-1.0-1.ezpkg" attachment);
3. Create a content for the new class, called "5023 Test 1", with the checkbox attribute checked. Publish;
4. Create a new draft on a new browser tab, for the new content, version 2. Leave page open on editing context, do not go for "Store draft";
5. Create a second new draft, on a new browser tab, for the new content, version 3. Again, leave page open on editing context, do not go for "Store draft";
6. A "Possible edit conflict - This object is already being edited by you." message will be displayed, indicating another draft already exists (version 2). Click on the "New draft" button, and then on the next screen, select version 3 from the "Current drafts (2)" list, and click on the "Edit selected" button;
7. Go back to the first draft (version 2), make sure the checkbox is still checked, and publish;
8. Go back to the second draft (version 3), make sure the checkbox is still checked, and publish;
9. A "Possible edit conflict - The object has already been published by someone else." message will be displayed. Click on the "Publish data" button;
10. Examine the content - the checkbox will be disabled, which is wrong.