Yes, it is not uncommon for Google to show 404 errors for products with URL changes, even if the correct new URLs are listed in the sitemap. This is because Google's crawlers may take some time to recrawl and update their index with the new URLs.
Typically, these 404 errors should eventually go away and stop being monitored by Google once the search engine has fully indexed and recognized the new URLs. However, the time it takes for this process to happen can vary based on the frequency of Googlebot's crawls and the size of your website. I am also facing this issue in my site flyer maker app and resolve this issue using the below techniques.
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Ensure that your sitemap is up-to-date and includes all the correct URLs for your products.
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Check for any internal links on your website that may still be pointing to the old URL and update them to the new URL.
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Use 301 redirects from the old URL to the new URL. For example, set up a 301 redirect from product old URL to product new URL. This tells Google and other search engines that the content has permanently moved to a new location.