Hello,
what do you mean by AMS Buffer please ? is it this part https://eu.store.bambulab.com/en-fr/collections/accessories-for-x1-series/products/ams-active-support-shaft-assembly
or this one : https://eu.store.bambulab.com/en-fr/collections/accessories-for-x1-series/products/ams-driven-support-shaft-assembly