I noticed a couple of weird thigs when waging war with the AI, and the AI actually loses:

1. When they are close to defeat, they offer peace treaties, wherein they ask me for money, resources, luxuries etc, even though they have no fleets / ships. Could that be a bug?

2. When the AI "forces truce" on you (a window pops up saying you can either refuse and lose influence or accept tribute) -- you can minimize that window and continue playing without making a decision. Then, if the AI starts actually getting dangerous, you can open one of these minimized windows and accept that truce they offered some time before. This definitely looks like a bug, but I'm not 100% sure, so I'm asking here.

First is a bug, second is not. You still have to accept or decline postponed treaty before ending the turn, so it's more like a loophole in diplomatic system of ES2.

About 2 -- actually, that's the problem -- I can end the turn without accepting or declining the treaty. So I can basically wait forever, and if things get bad, I can pick up an old treaty and accept it.

Here's a sample save file: bummer.sav

It's not possible to discern the exact turns when these treaties were offered, but it's clearly visible that there's two from lumeris and two from cravers