Unvented basement sink sewage smell

[Tsimeone]

Long story but i have an unvented sink and toilet in my basement. The sink has an AAV. We started to notice a sewage smell. It also has a trap and one of those slinky accordian like pipes to move around a drawer. Any advice?

 

[Terry]

A picture would help.
Sometimes it's just replacing the AAV, they can go bad.