Did you receive additional chat logs with the Reform Card of the second chat restriction? Also, was the second chat restriction for a 10 game or 25 game length? The usual progression, in that short of a time frame, would be to move from 10 games to 25 games. If you were given back to back 10 game chat restrictions, then that does sound like it might be some sort of system error, and you may want to send in a ticket to Player Support to ask them if they would mind looking into it for you.
However, if you were given logs of different matches than those on the first chat restriction, and it went up from 10 games to 25 games, then it probably was not a mistake and was likely a punishment handed out by the IFS. As some of the others have said, you can still earn punishments while serving a chat restriction. If there were instances where things were said, and reported, and the system judged them to be toxic, then yes, it can issue an additional chat restriction very shortly after the first one ends. Players can also earn a 14 day suspension if they continue to show escalating toxicity over a short time period while serving a 25 game chat restriction.