Under Kentucky precedent case law, to set aside a default judgment, good cause must be shown to the court.
To show good cause, and thereby justify vacating a default judgment, the defaulting party must: (1) provide the trial court with a valid excuse for the default; (2) demonstrate a meritorious defense; and (3) show the absence of prejudice to the non-defaulting party. See First Horizon Home Loan
Corp. v. Barbanel, 290 S.W.3d 686 (KY Ct. App. 2009).
You ask whether the court has discretion to set aside default if service is found to be proper. The answer is that if service is proper, then the defendant needs a valid excuse.
It's insufficient to merely show a mistake, inadvertence or excusable neglect. The excuse must be of the sort that is beyond the defendant's control (serious injury or illness, interference by a third party -- or the plaintiff, etc.).
BotXXXXX XXXXXne, the court's discretion is highly limited. The judgment will not be set aside absent a clear and convincing reason for the failure to answer timely.
Re contacting the court to examine the procedure, the plaintiff can contact the court, but I wouldn't expect a useful answer, because the clerk isn't going to volunteer that the proper procedures weren't followed. It's up to the defendant to prove that there was some defect in process that caused the failure to answer. In my view, this makes is somewhat unnecessary to try to find out what happened. Better to wait and see what the defendant claims as the excuse.
Please let me know if I can be of further assistance.