Synthetic textiles are a major contributor to funky smells in my experience, and I wasn’t aware of it until a few years ago. Sheets especially (microfiber sheets are disgusting, I regret ever using them), but also window shades, couch pillows etc. They can smell nasty, and it’s a kind of lowkey rotting plastic smell. Gross. I’ve switched to as many natural textiles as possible (been on a huge linen kick lately) and my place seems much fresher.