Hi Joe,
Sounds like a bit of a performance issue, but can't be sure with the very limited information you've shared.
Could you share the following:
Moodle version
Question type used (drag-drop text, drag-drop image, ...)
If an error message was displayed, which one?
On the learning design side of things: I'd recommend having a good look at building a question with 40 (!!) answer boxes in the first place. Unless you wanted to create a jigsaw type of question, 40 distractors and landing spots sounds like too much to me.
In those cases it may be better to break the question down into various ones, so your learners have an optimized learning experience.