Error "You cannot apply and post an entry to another entry with an earlier posting date."

Hello,
One of our customers using version BC 28.2 is receiving an error message when attempting to post a payment reconciliation journal: "You cannot apply and post an entry to another entry with an earlier posting date. Instead, post payment XX and then apply the result to invoice XXXXXX."
In this case, the payment is indeed intended to be posted with an earlier date than the purchase invoice it is meant to settle.
I’ve done some research, and this error message is a known issue. However, I haven't seen it appear in the context of payment reconciliation journals before; usually, it comes up with cash receipt journals or similar. Advice often suggests posting the payment first and then the invoice, but that isn't an option here since the invoice has already been posted.
Unfortunately, I cannot identify the payment number referenced in the message (though I can identify the invoice number).
In a sandbox copy of the environment, I tried a "quick and dirty" fix by setting the transaction date in the relevant line to match the invoice's posting date. The posting preview now runs without errors, but I’m not sure if this is the right solution. I think it would be better to unapply the entry—that option is available, after all. The problem is, I don't know what to apply the invoice from the error message against. As I mentioned, I can't find the suggested payment number anywhere.