For gethttpsforfree.com, I request all the needed nonces (GET /directory) after Step 2, and they get used through the remaining steps. So if things start to roll over before you get done, that might be the issue.
Based on current usage volume I'd estimate we start rolling nonces out of validity inside of ~1-2 hours for production. Since your requests were ~4 hours apart the nonces had expired. I think the ultimate take-away should be to view the bad nonce errors as non-fatal and have your systems recover by refreshing the nonce used.
-[Intermittent badNonce errors - #12 by cpu]
@cpu That was 9 months ago, so is the rolling time limit now?