Problem using REST to update page

I am having a problem updating pages using the rest api. I can successfully create and populate all fields and deleted page, but I am having problems editing all properties of a particular page type. I can edit the document fields, but not the custom field created particularly for this page type. To make matter more confusing, I have inherited another page type from this page type and I can edit it fine. The only difference I can see between this page type and others, is this one had it's code name changed very early in the setup of the site so the code name doesn't match the prefix of the table name in SQL. Some background as to whether this is a known issue would be great.

Cheers, Brad

FOLLOW UP:

Resolved!!

I was inadvertently nulling the page type item ID when sending the request data during the edit process.