Some sunny day you may come to this situation where the delete item option from ribbon is working fine but on the same list, the context menu delete item option for any list item is giving access denied.
The cause is due to the fact that the context menu option uses remoting to access this functionality where as the ribbon option doesnot. Due to this both are covered under different permissions in sharepoint. The ribbon option needs “”Delete Items”” permission, but the context menu option additionally needs the “”User Remote Interfaces”” permission.
So the solution; go to permissions for the problemed user and assign him/her the “”User Remote Interfaces”” permission.