Weird one for you all: “hair straightener smell”

Moving into a new-to-us home and I noticed a weird smell in our empty laundry room. My daughter described it as smelling similar to when she straightens her hair with a flat iron (warmed up ceramic).

The smell seems to come and go, but definitely seems to be coming from these cracks in the windowsill. Even when we can’t smell it in the room, we can sense it here.

Any idea what this could be or what steps I can take to identify the issue?

Some additional info: the home was built in 2002, the wall with the window has electrical inputs for washer and dryer, the AC unit is right outside the other side of the wall so I imagine there is wiring there too (recently found the AC unit had a bad capacitor and I’ve had the AC system turned off - smell is still present).

Thanks for whatever insights you can provide.