Insurers in Kentucky and New York, for example, say they’ve received flawed 834 enrollment forms from their local exchanges, though the extent of the errors is unclear. Washington state has already had to correct thousands of 834s with faulty information about federal tax credits.

Several state exchanges waited until late last month to even start sending application data to insurers, meaning potential errors haven’t had much time to surface.

At the least, these issues run counter to the popular storyline: that states’ enrollment systems have vastly outperformed the Obama administration’s effort. At the worst, they could endanger coverage for thousands of people who think they’re already enrolled for the start of 2014.

“While there is significant variation from state to state, health plans in many state-based exchanges are seeing similar problems with enrollment files,” Robert Zirkelbach, spokesman for America’s Health Insurance Plans, said Thursday.