Not in every game I've played but in a lot. When I establish a trade treaty with either and minor or major race, my home planet doesn't seem to have a trade route button but the destination planet does. This means I cannot use the treaty.

I haven't actually used trade routes before as I concentrate on ensuring the buildings all work correctly, but not being able to sort out trade routes definitely isn't right. I'll give Mike a nudge about this bug.

Trade routes are not available for all systems. I forget the exact number, but I believe you get one trade route per 100 or 150 units of population in a system. If you have less than that, you'll need to grow your population before you have any trade routes available.

Oh, the same system was in BOTF. I didn't realise it would be that simple...

To my knowledge, there has only ever been one bug related to trade routes: in earlier releases, there was a bug in the code for adding new trade routes. It mostly manifested itself when you built structures that offered a bonus of "+n Trade Routes". If you had a structure that offered +8 trade routes, it would only create around 4 new trade routes. It's been fixed in the latest updates, though.