I played with Carthaginians and Swahili in my last game. Swahili Legacy Trait gives +10 Stability on harbours per adjacent regular districts and this applies to both standard harbours and Bandari (Swahili Emblematic District) as shown in screenshot below. However, Cothon doesn't produce this bonus, also shown in second screenshot.

Save file:

Turn 048 - Germans - Era VI Stars Ready.ctr

Turn 053 - Germans - Advance Era VI Contemporary w Japan.ctr

EDIT: Same issue happens with Naust as well.

Glad to report that this is fixed now in Bolivar Beta. Cothon provides every bonuses related to harbours as well. Nevertheless, there's a new problem now. Bandari is counted twice as harbour and produces twice the stability than it should. Not that I have any objection to this mistake but I have to report it anyway. After all more stability never does harm :)))

Tooltip for Bandari says "+10 Stability on Harbour...." and "+10 Stability on Bandari...." If this is intended I'm all for it and thank you! :))))

Bandari and Cothon should be providing a total of +20 Stability in this placement.