(Pocket-lint) - Microsoft still has some explaining to do.

Last week, Consumer Reports announced it removed its recommendation badge for Microsoft's Surface line, which led to Microsoft issuing a response that essentially dismissed Consumer Reports' decision. But now, thanks to an internal memo that leaked out, we know that some Microsoft Surface devices had problems at launch, and those issues probably impacted Consumer Report's findings.

Consumer Reports surveyed 90,000 tablet and laptop owners and found that about 25 per cent of Surface users  ran into problems by the end of their second year of ownership. Paul Thurrott has sinc published an internal memo that shows high Surface Pro 4 and Surface Book return rates. The memo included a chart that puts Surface Book around 17 per cent, in terms of return rates, around its launch.

It stayed at 10 per cent for a half a year. But that's not all: Surface Pro 4 return rates hit 16 per cent around launch, but then dropped below 10 per cent after about a month. Surface Pro 3 had an 11-per cent return rate that dipped below 10 per cent to 5 or 6 per cent, where it has stayed since. As for the Surface Book, it had higher return rates than any other Surface device over the past two years.

Now, as a result, Thurrott claimed that Microsoft CEO Satya Nadella was concerned enough with the Surface Book's performance that he met with Lenovo sometime last year to see if it noticed any Skylake chip problems. Lenovo "was confused", as "no one was having any issues". Microsoft’s Surface Book problems therefore might be because of Microsoft itself, or rather, the device's custom firmware and drivers.

Other hardware makers could fix any issues immediately, while Microsoft had a delay. That would've impacted reliability, and as a result, its return rates, which Consumer Reports picked up on. All that said, Microsoft’s leaked memo was written by Surface chief Panos Panay. In the memo, he noted that Microsoft has “worked tirelessly” to fix the Surface Book and Surface Pro 4's problems since launch.

Microsoft thinks it has fixed all the issues. In fact, according to the memo, return rates have decreased over the past year.

Paul Thurrott
Writing by Elyse Betters.