Error: Target Name Invalid

has anyone ever received this error upon retaliating to a challenge?

In this case, I fought a challenge and retaliated. Enemy fought my retaliation challenge, then re-retaliated; when I fought that and won when I clicked “retaliate” it gave me the error message (pretty sure I remember it correctly) “Error: Target Name Invalid.”

I did this twice, just be sure it was not a one-time fluke.