Google "Redirect URI Mismatch/App sent invalid request"

Hi, I've just started using Cloudflare and we're in the process of migrating our web-app (Next.js 14) from Vercel to Cloudflare. My application uses google oauth for logging in the users. The problem is I keep getting the above error (even after adding javascript origin and all possible values of redirect uri from the google cloud console). It's an on-off problem, it occurs most of the times but 1 out of 5 attempts will somehow work and I will be able to further interact with the app. I don't know what the problem is. The same Google oauth client id being used through vercel for the same project and it seems to be working fine. btw, this is happening for both: https://random-cloudflare-code.app-name.pages.dev https://demo-custom-name.company-name.app (i also added a CNAME record for this on our namecheap domain to test if this would work but it didn't). Kindly help me out, please. Thanks!