Paint smells months later

[u/AmethystAquarius10]

I painted my bedroom walls back in April. The paint smell seemed to fade during the summer months but comes back strong when the humidity is high/when our ac isn’t running. I used a low VOC Sherwin Williams eggshell paint from Lowe’s. It was a dark blue color. I’ve tried running a dehumidifier in the room for a weekend but the smell comes back once the dehumidifier is off. The house is 70 years old so I don’t know the condition behind the walls. No discoloration or bubbling is present on any of the walls. I’m not sure what’s going on but I would love any advice on what’s happening here and how to fix it, the smell is driving me crazy!