They are being rehabbed, but it's all private enterprise. The three flat apartment buildings that were a cornerstone of low to middle class housing for a century are being gutted and rehabbed into $1.5 million single family homes. There is less and less middle ground all the time, it's either a dump or a palace. Gentrification powers forward.

It's nearly impossible at a local level to tax your way to sufficient funding to buy and rehab housing. It's further complicated by who owns it, if the city just covers rehabbing without owning the building, but it belongs to a slumlord, you can bet they will evict to current occupants or turn their property into an air bnb.

None which is to disagree with the assertion that raising home quality enhances safety and quality of life outcomes. I have a pet theory that if we made sure everyone had adequate air conditioning, the summer crime spikes would all but disappear.

Had a similar issue and for me it was that the vent was cracked inside the wall, leaking sewer gas into the living space.

The bulbs are probably fine and taking them out and putting them all back in will likely make things worse. Look for a Light keeper repair gun at the hardware store (Home Depot has them in the US) and follow its instructions to the letter. Make sure you get the right type for incandescent or LED per what you've got.