RHDG's Redis protocol implementation implements its own case insensitive string comparison instead of using standard libraries to do so.  And does it wrong.

server/resp/src/main/java/org/infinispan/server/resp/RespCommand.java

               if (upperByte == targetByte || upperByte + 22 == targetByte) {

Lower case ASCII letters are 32 higher than upper case, not 22.

So if a Redis client sends upper case commands it will work, but if it sends lower case commands it will fail to match the command, ending up with a TRACE log like:
[org.infinispan.server.resp.RespDecoder] Received command: null with arguments []