Zend certified PHP/Magento developer

Magento 2.4.4 – Elasticsearch sku autocomplete stop after 3 symbols

We are using ElasticSearch 7.

STEP #1 : we type the first 3 characters of a SKU in the search engine, we get many product suggestions

STEP #2 :we type 4 characters of a SKU in the search engine it says “Sorry, nothing has been found for …

In our test, we only use SKUs related to online products, products that Elasticsearch was suggesting in step #1

Any suggestions?

Thank you for your guidance