Hello,
My apologies for the delayed response. Concerning this issue, it is most likely it's an issue with either your, or your opponent's connection. Please let me know, by "before the match started" you mean, battle opened, but before passives applied, or before the battle has even loaded properly?
Also, if you meet those issues again on Friday's Matsuri, please try to get screenshots of the error messages, and when they occur :)