Amazon.com Inc.’s second annual Prime Day is producing similar year-over-year sales results in the United States, according to data from ChannelAdvisor Corp., which facilitates sales on online marketplaces such as Amazon.

Marketplace sales of ChannelAdvisor customers as of 5 p.m. Eastern Tuesday are “in line” with where they were on Prime Day last year in the U.S., and up 12% over Prime Day 2015 in the United Kingdom, ChannelAdvisor says, noting that promotions started at 3 a.m. Eastern time with many deals scheduled for afternoon in the U.S. “It looks like Amazon has spread out the deals more,” says Scot Wingo, ChannelAdvisor executive chairman. The 12% growth in the U.K. is unlikely to change given the late hour there, he says.
ChannelAdvisor’s data does not include Amazon’s sales in which Amazon is the retailer of record, which means such products as the Echo, Kindle, Fire and others that had significant Prime Day promotions were not factored in.

An Amazon spokesman says Prime Day year-over-year sales for third-party marketplace sellers in the U.S. and worldwide are up notably. “Led by strong growth internationally, we are seeing more than 30% increase over last year in the number of items sold by small businesses and sellers (which is how Amazon defines its third party sellers) on Prime Day,” the spokesman says. “We are expecting a record day for small businesses and sellers on Amazon with many more deals to come today.”

So how are the deals? Retail and e-commerce pricing analytics firm Boomerang Commerce analyzed 27,721 Prime Day deals offered during the first 10 hours of Prime Day. Boomerang found that 15.3% of all deals offered were for 50% or more off the list price that Amazon sets and nearly half (49.5%) of all deals were for 10% off.

The day has not been without headaches for Amazon, No. 1 in the Internet Retailer 2016 Top 500 Guide, however.

“We’ve seen reports that Amazon is having issues with its add to cart functionality,” Wingo says.

Amazon acknowledged those difficulties in a tweet at 8:40 a.m. Eastern: “Some customers are reporting difficulty with checkout. We’re working to resolve this issue quickly.”

Meanwhile, in an Amazon sellers’ forum, some users say the sale has been lackluster so far.

“This year does not appear to be as strong as last year,” one seller writes. “We are up about 30% today however it is still really early.”

“I have seen no spike at all so far,” another seller writes.

E-commerce analytics vendor Clavis Insight writes in an analysis that only eight of the first 100 Lightning Deals on Prime Day sold out during the first half of the day compared to 40% during the same time on Prime Day last year.

“Amazon and brands may have been caught off guard with the Prime Day demand spike last year, when the number of deals selling out quickly may have created a sense of futility and frustration instead of a sense of urgency among shoppers,” Clavis writes. “This year, they were clearly prepared with more products and deals available to meet Prime Day demand.”

Want a quick fact sheet on Amazon Prime Day from 2015 and how it compared to all other major e-retailing sale events?