After refusing for weeks to detail the extent of back-end problems with, the Obama administration on Friday said a technical bug affected approximately 25 percent of enrollments on the federal exchanges in October and November.

Those technical bugs, separate from the troubles consumers had experienced accessing information on the website during the first two months, are posing a significant new problem for those who signed up and are expecting insurance coverage come Jan. 1.

One in four of those applications either did not get transferred to insurers, were transferred in duplicate form, or had major errors in information shared.

Insurers are supposed to receive the 834 Forms from The forms, meant to be read by computers, provide insurers with information on enrollees and what plan they have chosen. Without the information, insurers have no way of knowing who has signed up on the Obamacare exchanges and what coverage they need.

A spokesman for the Centers for Medicare and Medicaid Services on Friday suggested that the only way those who enrolled in October and November can be sure they will be covered in January is by paying their insurance bill and contacting their insurer to confirm their standing.

“I would certainly encourage any consumer that has a question of their insurance choice to contact the insurance company of their choice to get additional information,” CMS spokeswoman Julie Bataille told reporters Friday.

Bataille said CMS, along with the outside firm QSSI, is working furiously to fix the back-end problems, and has succeeded in reducing the number of erroneous 834 Form communications to insurers to 10 percent of all applications.

That error rate could still be affecting a significant amount of applications, especially considering that is operating much more smoothly this week and has seen its traffic spike.

“To be clear, we do not have precise numbers [of those affected] at this time,” she said.

Bataille said more than 3.7 million consumers had visited over the past five days since the administration’s self-imposed Dec. 1 to stabilize the website and provide a smoother user experience for the vast majority of visitors.

“This week the site remains stable and experienced no unscheduled down times ... and page response averaged well under one second,” Bataille said.

Those running set up a queuing system that allows users to submit their email address and receive alerts about different times to enroll when the website is operating better. Bataille said officials offered that system once on Monday morning during a high-traffic time and another time on Tuesday afternoon.

She said all of those users contacted were invited to return on the same day and more than 93 percent actually did return to the website.