Wellcome onboard .This is a very well known issue on some Asobo planes like A320 that I mostly fly.There are many threads in the forum about this problem. See by reference the following: Default Airliners Lose Navigation Upon Reaching STAR and https://forums.flightsimulator.com/t/do-airliners-still-lose-stars-in-su10/542676
There is nothing that we can do .Hopefully Asobo will fix this problem soon.