When creating a transaction to either transfer funds or process a payment (either from a customer or to a vendor) the resulting transaction does not follow the normal sorting rules and always defaults to the beginning of the day on which it is posted. Such transactions also do not change their sort order when utilizing the NUM field for this purpose.

Steps to reproduce:

Enter three transactions in the following order using any single asset account for all three, say "Assets:Current Assets:Cash" :
1)An expense
2)A Transfer of Funds, using either the Transfer toolbar button, the Transfer entry in the Actions menu, or the keyboard shortcut — ⌘T.
3)A Payment using the business features, either from the Business > Customer/Vendor > Process Payment menu entry, or from within an invoice using the Pay Invoice button.
4)Open the account register for the chosen asset account and observe that the order of the transactions does not match the order in which they were entered.
5)Attempt to manually sort the transactions by entering in the NUM field a "1" for the Payment, a "2" for the expense and a "3" for the transfer.
6)Observe the sorting order does not change for any of the Payments or Transfer transactions. (if multiple expense or otherwise manual transactions were entered, ALL of those will sort according to the NUM field, the Payment & Transfer transactions will remain at the beginning of the day)

Transactions which DO sort properly:
1)manually entered transfers. (those NOT using the Transfer Funds dialog)
2)manually entered payments which were later linked to bills or invoices using "Assign as Payment" in the context menu.

A noted workaround is to reset the date of the offending transactions. They will then sort properly.

A discussion of this bug as well as the possible cause of this errant behavior is in this gnucash-user thread: http://lists.gnucash.org/pipermail/gnucash-user/2017-May/070525.html