I wanted to clarify a couple of things about my original question: (1) we are in the midst of delving into the facts surrounding the timing of when the distribution was directed by the plan sponsor and when the actual distribution was made. Therefore, it is likely that the interval between the date the distribution was directed and the date that the distribution was actually made could be much less than a few months.
I recall that earlier in 2025, there were some wide swings in the securities markets resulting from a great deal of uncertainty and complete confusion about the short-term and possibly long-term direction of the global economy which likely caused dramatic swings in value. Luckily, for those not taking distributions, history has shown that, over the long haul, investing in the equity markets not only evens out any short-term spikes in losses but far exceeds the rate of return over any other investment vehicle, notwithstanding the Great Depression. However, it is a frequent occurrence that the timing of a participant's decision to request a distributions when the market is at a high point and the time it takes to process the payment could include very sharp downward swings. It is hoped that if there are substantial upward swings during the period between the initiation of a distributions and the participant's receipt of the payment, in an involuntary cash-out scenario, that the fact that the value of the account balance upon receipt of the distribution being in excess of the involuntary cash-out threshold would not be considered an operational failure.
Regarding correction, Rev. Proc. 2021-30, Appendix A, .07 deals with situations in which the distribution is made without the participant's (and, where applicable, spouse's) consent. However, it is not helpful as applied to a 401(k) plan in which the only distribution option is a lump sum. The prescribed correction method is an after-the-fact consent, an election to receive distribution as a QJSA or the distribution of a single sum equal to the present value of the survivor annuity payable upon the participant's death. The problem is that annuities are not an allowable form of distribution under the plan and the participant has received his/her entire account balance. It would be hoped that when the IRS ever gets around to superseding the Rev. Proc. in light of SECURE 2.0 and other recent developments, it would allow the plan to merely seek an after-the-fact consent from the participant. The reason I said tender is that the participant may decide that since s/he got the money, it is a useless gesture to sign the consent form.
I apologize for being overly wordy here, but I felt that these points were important to add.