Coles listed a $130 case of bourbon at $27. The website went down and the orders were cancelled.
In May the Federal Court found Coles had advertised discounts that were not real, and its terms let it take back one that was.
Coles listed 24-packs of Jack Daniel's and cola at $27 on Friday.
They normally sell for $130.
The drinks are sold through Liquorland, the Coles-owned chain that supplies alcohol through the supermarket's website.
A Reddit account run by the operators of the price tracking site CW Scanner posted the listing on Friday.
"Found this. I'm assuming it's a mistake?!" it said.
The post has since passed 180,000 views.
CW Scanner then found the same fault across the range.
At least 20 cartons of beer and 46 cases of premixed drinks were affected, with 24-packs dropping to roughly what a discounted four or six-pack costs.
The average saving on beer was about $49. On premixed drinks it was $111.
The biggest was a 24-pack of Smirnoff Crush Mango and Peach, down from $202 to $29.
None of it appeared on the Liquorland site itself. One shopper reported getting the price matched in a store.
By Saturday morning the Coles website and app were both offline.
The site came back in the afternoon with the beer and premixed categories missing, went down again, and was up about 4pm.
Shoppers on Reddit began posting that their orders had been cancelled.
A Coles spokesperson said the company was aware of a technical issue and was restoring services.
"Due to a technical error, select 24-pack beer and RTD [ready-to-drink] products were incorrectly priced," they said.
Anyone charged would be refunded through the normal process, and the company apologised for the error.
That is Coles's right. A retailer does not have to honour a price it did not mean to set, and the terms say so.
It is worth holding the two things side by side.
In May the Federal Court found Coles broke consumer law with its Down Down promotion.
The ACCC took it to court over 245 products. The court found Coles made false or misleading claims on 13 of the 14 sample price tickets it examined.
The products had been marked up before they were marked down.
Judgment on a matching case against Woolworths is still to come.
Guardian Australia has also reported, using CW Scanner data, that promotional prices at Coles and Woolworths have switched on and off largely in step for the past two years.
So there is a two-year record of discounts moving in time with the competition, and a promotion the court found was not a discount at all.
Then there was one Saturday where the price really was 80 per cent off.
It lasted a day, it was an accident, and it was taken back before the weekend was out.