People who bought this sofa

The mistake

The recommendation box is built by pulling every other line item from baskets that contained the current product, with no filtering on the results. Ubiquitous low-value add-ons like carrier bags co-occur with everything, so they dominate every product's recommendations. Excluding the bag doesn't fix the underlying query — it just promotes the next most common co-occurring item, which for single-item baskets is the product itself, because the source product was never excluded from its own results.