Sewer Smell in High Rise Apartment

I rent an apartment in a new high-rise and I´m on the 15th floor. Weird smells are in both of my bathrooms, with one being a lot stronger burdened with smell than the other.

In irregular patterns there are foul, sweet sewerish smells rising up around the area of the toilet and they make the whole room really smelly. And then on other days chemical odors are coming in the bathrooms and even affect the neigboring 2nd bedroom.

What has been evaluated.

1. Maintenance told me to water the p-traps, which I do on a daily basis. But this doesnt solve the problem. Smell continues to come.
2. A plumber came and inserted a camera into the pipe under the sink. He said everything´s fine with the pipes.

Maintenance and community management are out of ideas. I am too. But smell keeps on coming in.

Does anyone has an idea what this can be and what to do?

Thanks a thousand. Quality of life really negatively affected 🙁