Could Not Reproduce Opponent Unable to Sideboard in-between Games

[Greater Clifford]

Today while playing in a friendly league, my opponent reported that he was unable to sideboard after game 1. He mentioned something about "don't found" (perhaps a "no sideboard found" message?).

Match #268393431
Game #876825058

 

[MTGO_TonyM]

We won't be able to investigate this via replay.