Heyyy Anthony P., Thanks for your response!
I believe the link you've shared will be really helpful. We've not set anything like that so most likely this is the issue
Update: we tried taking our frontend down and deploy only the phoenix UI, it worked but when we tried both frontend(react) and phoenix UI, it's giving this error
Our assumption is that maybe both UI are conflicting with each other and we've to find a proper solution for nginx or we've to deploy frontend and phoenix UI on different ingress