Manual sorting freezes a collection at the moment you arranged it. When a product sells out, it stays exactly where you placed it, so shoppers keep landing on items they cannot buy while in-stock alternatives sit lower on the page. The only fixes are constant manual upkeep or automated sorting that reacts to inventory changes on a schedule.
What the frozen-order problem actually costs
The damage is concentrated where it hurts most: your top positions. Those first rows get the bulk of views and clicks, and a sold-out product sitting there earns impressions that convert at zero. Shoppers who click through to a dead product page lose momentum, and some leave entirely. Meanwhile the in-stock product that should be in that slot is three scrolls down, invisible. Every stockout quietly converts your best real estate into a wall of unbuyable inventory until someone notices.
Why hand-maintenance does not scale
Fixing one collection after one stockout takes a minute. But sellouts do not schedule themselves, restocks reverse them, and a store with dozens of collections and steady turnover generates re-sort work daily. In practice nobody keeps up, so manually sorted collections drift further from reality the longer they live. The stores that feel this worst are the ones doing well: fast sell-through means fast staleness.
What inventory-aware sorting does instead
Automated sorting re-checks the collection on a schedule, demotes out-of-stock products to the bottom, and brings them back when inventory returns. A configurable inventory buffer goes further and treats nearly-gone products as gone, so a product with one unit left in one size does not occupy row one. If you still want certain products held in fixed spots, pin them and let the automation sort everything else around the pins.
Dynasort automates this. Install it from the Shopify App Store or see how it works.