For Medicare’s 61 million or so beneficiaries, Saturday marks the day that their coverage for 2020 is locked in — sort of.

The fall enrollment period, which opened Oct. 15 and runs through Dec. 7, is when you can make certain changes to your Medicare coverage, effective Jan. 1.

That includes going from original Medicare (Part A hospital coverage and Part B outpatient care) to an Advantage Plan, or vice versa. You also can switch from one Advantage Plan to another or from a standalone Part D prescription drug plan to a different one. If you take no action, you’ll automatically remain enrolled in your 2019 plan.

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However, you might be able to change your coverage after the calendar flips, depending on your situation. And this year, due to some reported snags with the revamped Plan Finder, there’s a chance you’ll discover something about your coverage that isn’t suitable if you used that online tool.

“That’s definitely something we’re worried about,” said Julie Carter, senior federal policy associate at the Medicare Rights Center, a nonprofit group. “There have been issues that have cropped up and we can’t be sure how often, how many people they’ve affected or how many people made decisions based on it.”

The Centers for Medicare and Medicaid Services, the federal agency that oversees the programs, has addressed all reported problems, which, Carter said, related to drug pricing. However, the concern is that users didn’t identify an issue at the time but will realize it later when, say, their prescription costs more than they thought it would.

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For Advantage Plans, there already is another enrollment period in place — Jan. 1 through March 31 — when you can make one switch, either to another Advantage Plan or to original Medicare and a stand-alone Part D prescription plan.

However, if you discover something wrong with your coverage that can’t be changed during that window, there may be another route. If it turns out that your choice was based on bad information, you might be granted a special enrollment period (typically two months) to change your coverage.

“As is the case every year, our call center representatives and staff caseworkers can help beneficiaries throughout the year if they believe they made the wrong plan choice because of inaccurate or misleading information,” according to a recent blog post by the Centers for Medicare and Medicaid Services.

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“This process isn’t new, but this year we’re doubling down on ensuring that it’s a simple and painless experience for beneficiaries,” the post says, providing 1-800-MEDICARE for those who might need help.

Medicare agents say it’s too soon to know if concerns about the Plan Finder will pan out.

“It will be interesting to see,” said Elizabeth Gavino, founder of Lewin & Gavino in New York and an independent broker and general agent for Medicare plans.