wrong state tax withholdings on pension

That state tax was actually withheld. There will not be a corrected 1099.

Taxpayer needs to inform payer to stop withholding state tax.

For 2022, file a nonresident MA return to get the withholding back.

You need to research how that source of the pension is treated by MA:

https://www.mass.gov/info-details/learn-about-tax-treatment-of-pensions-in-massachusetts#nonresident-pension-distributions-

You've made a couple of assumptions that the 1099-R is wrong (it's reality) and that this isn't taxable in MA. If the 1099-R has the right address for your taxpayer, then someone knows this person no longer lives in MA, and that's not likely the issue.

There is no way for the pension payer to know where a person resides, just by their mailing address. Mom could be in a nursing home in Massachusetts but getting her mail at son’s home in Vermont. But the federal law is clear that states can’t tax pensions paid to nonresidents.

4 U.S. Code § 114 - Limitation on State income taxation of certain pension income
(a) No State may impose an income tax on any retirement income of an individual who is not a resident or domiciliary of such State (as determined under the laws of such State).