I have noticed a similar issue with my recently installed Sewer Ejector. However I have noticed that the plumber connected the Toilet and Tub into the Main Intake within the Ejector housing, yet they tied in the Sink to drain into the Vent Intake Pipe.
Do you have a similar configuration? I am currently investigating a second opinion as to whether or not this is an acceptible connection. To have the sink drain into the Vent Pipe connected to the Sewer Ejector housing.