After updating to 19.15.x a .net application is not able to retrieve data with dates

We had a successful dev and test update path from 12c to 19. However in prod we have an issue where dates are not longer being returned correctly for another vendor application to read them. However we were able to do the same against a test db with the prod software and the issue isnt present. Is it possible we are missing parameters that could be causing this issue? Or is there a way to test the environments or at least break a test env to be having like prod. We did attempt to break