Steam achievements broken

Brief description of the issue:
I have completed some achievements but they didnt get done in steam. Im not sure why. For example this one:
World Traveler
Land successfully at 500 different airports.
12 / 100

I have landed at more than 12 airports, in fact i think its over 50. I have history and videos as well. I just dont know what happens, some work some dont.

Good discussion thread:

e.g. points to:

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