It is my understanding that because elections must be made every year for Section 125 plans, the correction would be in that year only as the election doesn't carry forward. There are no balances to test, only elections vs wages, and pre-tax elections are tested within the year. And while a plan can have a very limited amount that can be carried over for FSA Medical only (or a short grace period where last year's elected $s can still be used), it is nothing like the amount that accrues in qualified retirement plans over many, many years with attached earnings. So there are no really ongoing future or deferred benefits after the end of the current plan year (NOTE: HSAs do NOT fall under this) So there are no trust earnings to be taxed should the Section 125 fail nondiscrimination testing. In the end, Section 125 plans do "restart" each year.....
I know this isn't a "cite" but is a really good explanation of Section 125 and their "every year" issues: https://www.sullivan-benefits.com/wp-content/uploads/Section-125-Cafeteria-Plans-Overview.pdf