Unknown format specifier "?"

[ondraasek]

Hi, I am getting this. Any idea why? Its Rust thank you
Unknown format specifier "?" {"exception":"[object] (ValueError(code: 0): Unknown format specifier "�" at /home/project/vendor/austinb/gameq/src/GameQ/Protocol.php:461)
[stacktrace]
#0 /home/project/vendor/austinb/gameq/src/GameQ/Protocol.php(461): sprintf()
#1 /home/project/vendor/austinb/gameq/src/GameQ/Protocols/Source.php(146): GameQ\Protocol->challengeApply()
#2 /home/project/vendor/austinb/gameq/src/GameQ/GameQ.php(458): GameQ\Protocols\Source->challengeParseAndApply()
#3 /home/project/vendor/austinb/gameq/src/GameQ/GameQ.php(357): GameQ\GameQ->doChallenges()