How do I correct missing departure records? [duplicate]

I am a Canadian citizen. A few years ago, I had a four-month internship in the US. I entered on a J1 visa. After completing it and returning to Canada, I subsequently did two more four-month internships, both on J1 visas as well. However, when I returned from the second internship, I completely forgot to turn in my I-94 card. When heading to the US for my third internship, the CBP agent obviously noticed this, gave me a big lecture on how I screwed up, almost turned me back home, etc.; nonetheless, he still admitted me and I completed my third internship, making sure to hand in the I-94 card this time.

Some time later, I went to the US for a short vacation. For some reason, I was pulled aside again for I-94 issues, even though I turned in my latest I-94 card. This almost caused me to miss a connecting flight.

I then found that there's an online database where you can check your arrival and departure records. To my surprise, it indicates that there are still two missing departure records, despite the fact that I am in possession of zero I-94 forms (I turned it in after internships #1 and #3, and the CBP agent took the one from internship #2):

                   Departure    2013 June 14        MIL - MILWAUKEE, WI
Vacation      -->  Arrival      2013 June 08        CHI - DISTRICT OFFICE 9, CHICAGO, IL
                   Departure    2012 December 23    SFR - SAN FRANCISCO, CA
Internship #3 -->  Arrival      2012 August 25      TOR - TORONTO, ONT. CANADA
Internship #2 -->  Arrival      2011 December 31    TOR - TORONTO, ONT. CANADA
Internship #1 -->  Arrival      2011 April 28       TOR - TORONTO, ONT. CANADA

I fear that these missing departure records will haunt me every time I try to travel to the US. How can I correct the missing records, even if I don't have the I-94 forms anymore? I still have all of my original boarding passes for the missing departures (all trips were done via air).