I think I finally "caught" Aeroplan doing what I suspected was going on for a long time...

For years I had a feeling that some transactions just disappear from my Aeroplan account. Checking the balance frequently - sometimes daily - I'd notice it going down a bit... but thought maybe I simply forgot what it was... it's not possible, how would something simply disappear.... and all recent transactions were still in place.

That's what I thought - and never took it seriously - until today.
This year I'm travelling much less than previously - and consequently have substantially less transactions. I booked parking at YUL three times since February - twice at Hotelpark, which should give 450 miles, and most recently at the multi-level parking, worth 350 miles.
When I arrived for my first booking back in February - I wasn't able to open the gate using my c/c - so called the attendant and she just let me in after verifying that I in fact paid for my stay. Upon exit another person let me out the same way. The booking didn't reflect neither the check-in nor the check-out - which, I know from experience, means that the miles won't be posted. So I wrote the parking CS an email 3 months later - and the miles eventually got posted a week or so after that.
I hope you believe me that I do remember seeing them on my account.
The second booking was on May 14. I was not able again to use my c/c to get in - a different one. But the assistant printed me a ticket with my booking number, which I used to open the gate. So this time - the miles showed up on the account promptly.
The third and last time was on May 29. This time the third c/c finally worked. I got the miles a few days later. I saw them several times checking the account.
Tonight I decided to check the account - and the first and the third transactions are gone! I am positive about that, I used the filter by Partner - definitely nothing except that transaction on May 14. And, like I said, there were not many other transactions for this year - so it's difficult not to spot something like that.
Of course I will call them tomorrow - and I'm Diamond btw - and ask. Hopefully they have a good explanation. Hopefully this is just a system glitch, they'd reinstate everything and apologize. But I am not sure if those are only two ones that are missing, or maybe there's more.