Hi again,
it seems you don´t have all WU updates installed … I have tested your example flightplan with both sim versions (official and beta) and the result is in both the same:
Here the loaded flightplan in the current sim version 1.32.7.0
… and here with the latest beta version 1.33.6.0
You see, exactly the same …
In nearly 99.9% its a missing WU, which is not installed (or not installed correctly). The reason why it´s so important to install all updates (incl. the World-Updates) is, that in these updates ASOBO/MS makes some changes on some airport ICAO codes (or they remove outdated airports) - the result is this north-pole issue. I can´t say why and what this has to do with a loaded flightplan but to install all WU correctly, the issue will be fixed automatically.
So, there is a unknown logic/connection between a flightplan which will be loaded with the WU. We have no possibility to look deeper what happened exactly (and why) that is only possible from ASOBO, sorry.
Again, to fix this - check, if you have all World-Updates installed. When not, that is the reason for the north-pole issue.
Hope that helps,
Richard