It is important to keep everything chilled to ensure the chicken mixture stays on the skewer without falling off.  Have a bowl of chilled water nearby while assembling the kebabs. Dip your hands in the cold water before handling the meat to help it adhere to the skewers securely.  The cold temperature helps maintain the meat's cohesion and reduces the risk of slipping off.  Additionally, please make sure the meat mixture itself is chilled before the assembling process.