Calls of frustration to the Minnesota Department of Natural Resources, along with emails and online comments, have made one thing clear about some aspects of its state parks camping reservation system:

There are hundreds of unhappy campers out there.

They are miffed at being unable to reserve prime summer dates at popular park campgrounds because others are taking advantage of a loophole in the system and overbooking.

The fallout has the attention of managers in the DNR's Parks and Trails Division, which oversees the state's 76 state parks and recreation areas. More than a million people annually camp there, and many of them want to return again and again to parks along the North Shore. Camping and lodging sites at six parks, such as Temperance River, Gooseberry Falls and Tettegouche, are among the most reserved systemwide this spring and summer.

"The issue has just ballooned," said Rachel Hopper, Parks and Trails visitor services and outreach manager and part of a DNR team working on a fix.

The state used to keep about one-third of the sites at the parks, first-come, first-served but went to a new all-reservable system in 2016 intended to ensure more access. The move increased campsite use by more than 6% in the first season.

Somewhere in the timeline of the DNR's move to make the system more equitable, the intended improvements went off the rails. And then some.

A glitch in the online reservation system allows campsite-seekers to sweep up more days than they should.

Campers currently go online to see what sites are available 120 days out. What some are doing frequently is booking 120 days out, plus 14 days more. The system unintentionally allows users to extend that reservation to two weeks on a single campsite.

"They are going into the system and gaming the system," Hopper said.

They also aren't always releasing unwanted days, leaving some campsites unattended on premium nights at high-demand parks. Users can cancel 14 days or longer in advance of their stay and get fully reimbursed, minus the nonrefundable reservation fee.

"We recognize that there is an issue there. We are actively talking about it and working on it," Hopper said. "We'll be rolling out the fixes in the coming year. Some will be more quickly implemented than others."

Hopper said the division is wary of creating more headaches for Minnesotans who just want to enjoy the outdoors. Exact measures remain undecided, and some might take longer than others.

Still, most changes will get implemented in advance of next year's busy season, while a few could happen yet this camping season, Hopper said. One possibility is a mechanism to more quickly identify unoccupied campsites and communicate the update to the public. Currently, staffers wait until 11 a.m. on the day after a scheduled arrival before opening a site for rebooking. Also, the division is trying to make it easier online for people to find alternative sites, with the ability to sort by availability. The interface update and new look could happen this week at the main reservation website.

"This should help user experience," she said.

Hopper stressed that overbooking is isolated. There are plenty of attainable campsites, even on busy weekend days, at most parks. And then there are the state forest options, less expensive and no reservation needed.

"The whole thing comes down to equity," Hopper said. "We want to make sure everyone has special access to these special places."