nova-api routes are returning 504 error in production

Hi,

We have a Nova admin will all of its pages working in our dev and stage environments. However, some of the pages stopped working in production with some of the nova-api/* routes returning 504 error.

Is there a well-known cause for nova-api/* returning 504 error? As the error/exception is not logged in storage/logs/* files, what debugging steps can be taken?

Thank you.