Sharepoint 2010 managed metadata service

We have a SharePoint 2010 farm consisting of 3 Web Servers and 2 Application servers.

The farm has 6 Web Applications and 3 Managed Metadata (MMD) Service Applications.

Each MMD service services 2 distinct web applications via membership of 3 separate proxy groups.

We also have 3 distinct User Profile services (UPS):

Web App                             Proxy Group

W1                                         ProxyGroup_A

W2 (mysite host)             ProxyGroup_A

W3                                         ProxyGroup_B

W4 (mysite host)             ProxyGroup_B

W5                                         ProxyGroup_C

W6 (mysite host)             ProxyGroup_C

ProxyGroup_A contains MMD_1, UPS_1

ProxyGroup_B contains MMD_2, UPS_2

ProxyGroup_C contains MMD_3, UPS_3

Each MMD service is associated with two web applications.

No web application is service by more than one MMD service or UPS service

The MMD connection for each MMD service is marked as thedefault store for keywords.

Managing the term store for Site Collections within any web application works as expected.

Creating and manipulating enterprise keywords doesn't present any problems and terms are created in the correct term store associated with the correct MMD service.

This issue we have is this: When navigating to a MySite and editing a user profile, any profile attribute that is of the enterprise keyword type (and therefore sourced via the MMD service) is disabled and marked with the following message "Edit profile - There was a problem retrieving data for this field. Updating values in this field is disabled temporarily. You can still update values in other fields".

If two of the MMD service connections have the "default store for keywords" option unchecked then the problem goes away for the MMD service still marked as default. This is contrary to the published Microsoft Documentation and the warning messages displayed on the MMD connection configuration pages.

The default connection setting appears to operate at the farm level and not at the Web Application level as stated in the documentation.

Under managed metadata service connection

If this service application is the default storage location for keywords

Then Warning: Another service application on this farm is already configured as the default. This feature will be disabled if multiple defaults are associated with a single web application

My question is – Is this expect behaviour for the configuration that we are using ?

Regards