He said July and August sales and bookings figures showed the company was ahead of the plan, then in September it had a shortfall which was not swiftly traced.
"Mid-September, we still only had July and August figures," Svanberg told "Power Lunch Europe."
"It's something for us to think about, if we can trace it better."
Ericsson's final third-quarter figures, released on Thursday, were broadly unchanged from preliminary numbers last week as the company confirmed operating income fell to 5.6 billion crowns ($865 million) from 8.8 billion a year earlier.
Ericsson shares were down 1.6 percent in afternoon trading.
The company repeated the reason for the poor results was lower sales of network upgrades coupled with a higher proportion of new network sales. Upgrades are more profitable, while new networks involve greater costs and hence are less lucrative.
The company said it still expected mid-single-digit growth for the GSM/WCDMA market in 2007, and its early expectation was that current market conditions would prevail in 2008.
The comments were broadly the same as issued last week.
"There's no fundamental change to the whole outlook," Svanberg told CNBC.
"I don't think we should dramatize the situation," he added, saying that operators had good, healthy financial positions and traffic increases were stable.
But the market is also concerned that Ericsson had not prepared it better for the weak earnings.
"Confidence has been further hurt by the fact that Ericsson had no inkling that things had gone so badly wrong just two weeks before the end of the quarter," said Nomura Securities analyst Richard Windsor in a note to clients.
Svanberg said the third month of each quarter tends to make up the biggest share of business. Rather than each month accounting for a third, it was more like 25-25-50, he said. He said July and August were doing well, and as of mid-September the company was not aware of a looming shortfall.
"We also want to understand why September was lower. If that was just a temporary thing, or if that is hiding anything in particular. But with all that said, the general outlook for 2008 with those comments hasn't really changed," Svanberg said.
Svanberg paid tribute to Sundstrom for helping turn the company round when the telecoms equipment industry was in turmoil.