I experienced a problem while I doing the chin stand, as my legs successfully lift toward the sky but the wheel not steady and a little bit slippery, is this situation common ? Thank you in advance.

Samantha老師您好:
想請問一開始瑜珈輪要放在腹部的哪個地方呢?是肚臍正下方，還是小腹正下方呢? 謝謝您。