How to track what's happening with a field?

I have one field, created with module Viewfield. Or just as a text field. Or whatever, actually, neither built-in nor provided work as expected.

So what's happening is:
I have 2 content types, let's call them Production and Test. Test is brand new, created to test this issue. Field works properly on Test, but does not appear at all on Production. I use our custom theme, rootcandy and garland for tests, so I'm pretty sure theme is not a problem. Something prevents additional fields from displaying no matter what theme I use. On the other hand, "Dev render" tab show this field all right. And Dev load if appropriate, consistently between content types (some of the fields I tried are display-only ones).

So my questions are:
1) What can prevent field from being displayed, if not a theme?
2) How can I track it?