Filed taxes already and corrected a 401K over-contrib. Employer now says they cant process payout by 4/15. Do i need to file an extension now? What is proper action?

I filed already correcting for the 401K over-contribution just like turbo tax instructed.

Now employer is saying they cannot guarantee that the funds will be withdrawn from the 401K account before the end of the day today.

Do I need to file an extension?  Am I doomed to be double taxed?  What is the proper course of action at this point?