The is an extra thread for achievment guides, https://forums.flightsimulator.com/t/achievement-guide-and-discussion/285425 Achievments have been pretty bugged right from the beginning, see link and other threads.
Not sure whether your problem was introduced with SU5 (1.18.13.0/1.18.14.0) or has existed previously.
Have you checkt OAT? That is bugged too and might prevent you from going fast.
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