It's a well known fact that some apartment owners are jealous when they know that your apartment is being leased for rental income. They will try all means to give you unnecessary troubles and make your life difficult.
Take for example my HDB. That bastard old man living directly below my unit made non-stop complaints against my tenants to the town council. They complained of noise from the dragging of chairs until my tenant was so kind that they replaced all their wooden chairs to plastic ones. They complained of the noise from the occasional pounding of herbs by my tenant but these were done during the day time and even with a thick book placed under the granite pounder, so what else does he wants? They complained that my air-con compressor is making excessive noise, but I challenged them to pay for the service check by PANASONIC Singapore and if it is proven to be within its allowed sound level, he will bear all the costs to PANASONIC Singapore. I have 3-monthly servicing contract and the technicians had even told me that it is within the expected sound level, considering that the compressor has aged a little. Even when I replaced my air-con system for the whole unit a few years ago, this old bastard immediately came up to see what was happening because there were of course some hacking and drilling noises. I told the town council that these works were done during the day time and on a weekday. So, I have committed no wrong.
Even my brother-in-law who lives 1 floor below me and adjacent to this bastard's unit (they never talked to each other), had put his son's rabbit in a cage next to his own gate, but this bastard also complained this practice to the town council. Eventually, I wrote a very strong-worded rebuttal letter to the town council to highlight all these unreasonable complaints from that bastard and I told the town council that I don't need my neighbor downstairs to teach me how I should live in my own HDB flat. And I further added that if he wants a totally quiet environment, he should move to a landed property himself. Thereafter, no more complaints from this bastard anymore. It all depends on how well you can pen your letter to the town council until they have no case against me.