We just moved in, and I’m now looking more carefully at the contract details. For example, it was mentioned that the maintenance fee would be included, but the bill arrived separately. And there’s a part that says ‘previously accepted increase’ which I don’t understand. Could the landlord have backed us into a corner with a clause squeezed in between? How can I check this?
I had an issue with the fee too. In the conversation, they said ‘included with this’ and then sent it separately. Did you check what it says on the contract? Otherwise, these things just remain in words.
If it clearly states the rental increase rate for the previously accepted increase (for example, 20% annually), you can legally link it to that. But if you don’t have detailed information, you can apply to the Consumer Arbitration Committee. As for the maintenance fee part, does it say ‘including maintenance fee’ there? If it doesn’t, your situation might become more complicated.
I once signed a contract without really paying attention, and these things end up being a real hassle later on. Why not ask the landlord directly about that ‘pre-agreed increase’ part? You’d get a clearer answer 
I’ll be honest, you have acted a bit carelessly. You need to read and understand the details thoroughly when signing the contract, especially in this day and age. It won’t help to later suspect that ‘there was this there, and that here.’
Do you know exactly how much the fee is? Were clear numbers discussed when negotiating with the landlord, or did they just say ‘included’ without elaboration? It’s hard to comment without knowing the details 
The “pre-agreed increase” section in a rental contract is usually a clause that the landlord includes to secure the annual increase. However, it cannot exceed legal limits. For example, the latest law set a 25% cap. If it exceeds this limit, you may have legal grounds to contest it. The rent is a separate issue, so pay attention to the correspondence.
I read the contract carefully again, and there is indeed nothing regarding the dues. However, in the ‘increase’ clause, there isn’t even a single number mentioned; it is written very vaguely. Is this legal? I’m not sure.
This fee issue is very common; they usually talk as if it’s not included, and then send it separately later. I think it’s more about how the system is set up rather than the landlord’s bad intentions. Of course, the ‘increase’ part is still problematic; you need to clarify that part urgently.