Is the n-20-29 IRS notice will help?
https://www.irs.gov/newsroom/irs-provides-tax-relief-through-increased-flexibility-for-taxpayers-in-...
"or to provide for an extended period to apply unused amounts remaining in a health FSA or a dependent care assistance program to pay or reimburse medical care expenses or dependent care expenses in a manner consistent with this notice must adopt a plan amendment.."
