So we can take it that you are using asynchronous code, so please refer to this page about working with promises in Wix Corvid if you have not already seen it.
https://support.wix.com/en/article/corvid-working-with-promises
Also, as you are using Wix Fetch, check that your code is correct there for working within the backend too.
https://www.wix.com/corvid/reference/wix-fetch.html
https://support.wix.com/en/article/corvid-accessing-third-party-services-with-the-fetch-api
https://support.wix.com/en/article/corvid-web-modules-calling-server-side-code-from-the-front-end
You can find out more with these links too.
https://www.andreasreiterer.at/single-result-with-promise-all/
https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Promise/all
https://alligator.io/js/async-functions/
https://medium.com/@SteelKiwiDev/asynchronous-javascript-programming-with-promises-8c9a3661ccc4
https://medium.com/front-end-weekly/callbacks-promises-and-async-await-ad4756e01d90