permission "access my cases and activities" is broken by CRM-21461
See https://civicrm.stackexchange.com/questions/25950/problem-with-civicase. CRM_Case_BAO_Case::getCases() used to return a list keyed on case_id. Now it returns a sequentially keyed list. I'm not sure if anything new is depending on the new keys, but since that seems unlikely, replacing "$key" with "$case['case_id']" around line 680 and later instances would fix this?