Bitrix table b_sale_fuser growing a lot?

Question

1C-Bitrix

Tell me how to track where the requests to write to the b_sale_fuser table come from. We
began to notice that records are constantly being written to the table, we do not have such a large project, there are not so many users who constantly work with the basket. every 2-5 seconds about 10-20 entries are written to a table of approximately 500,000 entries, the agent for deleting old baskets works, cleans old baskets in 7 days. But apparently there is a completely different problem here.

SELECT u.ID, b.ID FROM b_sale_fuser u
LEFT JOIN b_sale_basket b ON b.FUSER_ID=u.ID
WHERE b.ID IS NULL
ORDER BY u.ID DESC

Found lines: 413 708
it turns out 413 708 zombie lines, it is not clear where they are written all the time.