There is a tactic called sniping. This is when the player times their troops/navel units to land right before your attack. This seems to be the case because your navel units were not sufficient to clear his.
P.S. Biremes are a defensive unit, LS should be used for offensive situations.
That isn't the case. He's inactive. I've been spying him for over a week to make sure. I just spied again and he as the same 6 bemires just like he did before. 6 vs my 16. If they are defensive units shouldn't my 16 have beaten his 6?
Well, I suggest submitting a support ticket then. (settings>support>ect.)
I'm telling you though, their is no bug. You did not kill all of the biremes so they sunk your biremes and about half your transports. The troops that did land on shore were not enough to clear the land units in the city.
if you test it with all factors its is correct. I include -30% luck in my sims to account for the worst before i ever send an attack. dont forget things such as battering ram and phalanx
You did receive BP but if you don't clear all of his troops it won't tell you that. Also, birs are not for attacking. They are only good at defending and that's why your birs and transports were sunk. Stick with light ships for attacking.