Edit online doesn’t save the changes made by a non-member of private site who has permission on the content

Edit Online action performed by a non-member private site user who has permission on the document, doesn’t save the changes.
This issue was tested with a user with “Collaboration” permission on the content.
“Public” site doesn’t have any issue. Document opened by edit online can successfully save the changes.

Steps to reproduce:

1) Start Alfresco Enterprise v5.0.3.7
2) Login to Share as admin user and create user “user1” or enable sample user “mjackson"
3) Create a “private” site for example “testsiteprivate”
4) Upload a Microsoft Office document to document library of this site (testOnlineEdit.docx)
5) Use Manage Permissions on document to grant Collaborator permission to “user1” (screenshot 01_alf5037_managePermissions.jpg)
6) From document details page copy the "Copy this link to share the current page" link (screenshot 02_alf5037_copyShareLink.jpg)
7) Logout
8) Login as “user1”
9) Paste link from step 6
10) Click Edit Online (screenshot 03_alf5037_nonMemberUserEditOnline.jpg)
11) Edit document in Microsoft Office (Word), save and close Office. (screenshot 04_alf5037_editDocInOffice.jpg)
12) Back in Share refresh the document details page in order to get the updated preview.

Expected behaviour: The document preview displays updated document.

Observed Behaviour: The document is unmodified.

Analysis to date:
The issue has been tested in different environments. The following environments show the same behaviour:

• Alfresco versions 5.0.2, 5.0.3
• Windows 10 with Office 2016
• Windows 7 with Office 2010 and Office 2013

Alfresco version 5.1.1 has a different behaviour:

• Copy of link to share the page (step 9) in version 5.1.1 doesn’t load the page and it displays message “Something’s wrong with this page…” (screenshot: alf511_sharelinkFormPrivateSite.jpg)

• Customer is using Alfresco version 5.0.3.7