Hello,
I had the same type of error, I do not know if it is the same case, but I found the source of my problem and it was that since I am using wordpress as a headless, I had put in the general settings -> Site address (URL), there I had configured the address of the front that was hosted in Vercel and when making calls to a custom API, it skipped the error, I hope it will help if someone has made this change.
Greetings
