Feeds Self Node Processor doesn't respect "Allow source configuration override" option on Xpath Parser

The option to "Allow source configuration override" on the XPath XML parser seems to break when using Feeds Self Node Processor.

Step 1: Under "Parser > Settings" I set up the XPath XML parser context and queries and select "Allow source configuration override".

I've tried two different set-ups which create the problem:

Step 2A: I create a Node manually. Changing the Xpath parsers context and queries as I need them. The Node updates correctly on save (and on selecting import). However, when I go to Node>Edit again the 'context' and 'queries' go back to the general context and queries as set up under Step 1.

Step 2B: I create a Node automatically using a spider. The Xpath context and queries as per Step 1 are correctly passed to the Node, and updated on Cron (or Import).
However, if I then repeat Step 1 and change the general context and queries - on the next Cron run the Node context and queries are over-written (for the already saved Node).

I hope this makes sense - thanks in advance for any help with this!