If your missions started to generate at long distances, it means that our in-game anti-abuse system was activated. This happens when you place too many stations of the same type within a small radius, which is neither realistic nor fair to have all these stations cluttered in one area to get new missions easy to complete.
The mission spawn radius this system triggers is up to 100 km distance.
If you then want your missions to spawn normally, you will need to move or remove stations that are standing too close to each other.
In order to maintain the integrity of this protection mechanism, we are unable to publish detailed information on how this protection is triggered.