Wrong results in Drag and Drop

This is the first exam I've done since upgrading to Inspire v11.3 with the new interface and I'm getting some weird behaviour from a drag and drop question. The scenario in question is getting the student to drag and drop words to fill in a paragraph (something I've used without issues in previous versions) however I'm finding that as soon as I add any drag items over the 3 that it defaults to, they automatically get marked wrong. I've switched this to provide immediate feedback to test it - when you drop the 3rd correct entry it says 'correct' and if you drop any more it says it's incorrect. Here's a screenshot of the settings - I've tested it with as many as 10 pairs, but I've kept it simple here with just 4. The first three will always be correct, no matter the order they are placed, but the fourth (and above) is always wrong.

[ATTACH=CONFIG]581[/ATTACH]

Any help would be appreciated - I might be missing something simple but I find this interface much more confusing than the old one.

Chris.