How to unload all goods?

Question

1C

Uploading goods to the site from 1C is set up.
The site is self-written, the script that processes the upload is also self-written.
Everything works well, new products are added, balances are updated.
But there is another problem. When a new product appears in 1C, or a product arrives that has not been there for a long time, then it is often not in the unloading for a long time. The error is not in the script. We do a full unloading and look at the resulting file. These items are simply not available. Sometimes they appear there immediately, and sometimes after a while. On what it depends is absolutely not clear.
Tell me where to dig in 1C (I don’t understand it myself)? Why doesn't she sometimes add them to the upload right away?