Calendar dashlet is blank on dashboard after upgrading from 7.4 to 7.5.1

After upgrading from 7.4 to 7.5.1 the Calendar dashlet is blank and frozen.
You have to logout and log back to display it but once you go to any other screen and go back to Home
it is blank and broken again.

Have you checked your log files for the CRM and also PHP?

Did the upgrade run successfully?

Have you re-set the correct permissions and run a Quick Repair & Rebuild?

Do you get any console/browser errors when trying to load the homepage?

According to upgradeWizard.log the upgrade went without errors.
Quick repair and rebuild did not help
No browser error. The initial home screen after login displays Calendar dashlet.
Subsequent returns to Home screen display blank dashlet
The corresponding Apache error log has an error which, I assume, has something to do with this issue
[Mon Feb 01 07:45:49 2016] [error] [client …] File does not exist: /var/www/sugarcrm/include/MySugar/javascript/AddRemoveDashboardPages.js", referer: http://…/index.php?action=ajaxui

P.S. The file itself exists with correct 644 wwws-data permissions

tail -f error.log displays the above error each time the Home page is reloaded.

Since initial load of the Home page with dashlets is OK and subsequent loads produce blank calendar dashlet, I assume this is something with ajax call ?


Firebug produces the following error when reloading Home page:
GET 200 OK 40ms
GET"text/javascript"%20src=include/MySugar/javascript/AddRemoveDashboardPages.js" 404 Not Found 14ms

BTW the Calendar dashlet is displayed in Firefox but not in Chrome.

@Will Any news on troubleshooting and fixing the bug?