Later this year I will be in Spain while my sister is in Russia. Just for fun I tried planning a route between these two countries and it didn't work. Further experimenting revealed even planning routes within Russia rarely works. Ridiculous trans-Europe trips like Lisbon to Helsinki (4,000 km) and London to Athens (2,000 km) work, but simple trips simply going from Eastern Estonia and Western Russia, right across the border, do not go through.

What's the deal?