in function sendChangeSpeed, before
msg.add<uint16_t>(speed);
add
std::cout << "[DEBUG] sendChangeSpeed - creature ID: " << creature->getID()
<< ", baseSpeed: " << creature->getBaseSpeed()
<< ", speed: " << speed << std::endl;
Once the server is up and running, any changes to your character's speed will be displayed in the console, allowing you to see if the issue is coming from this feature.