Just to be clear. If you are low where correction takes place and go from idle to any bigger distance there will always be 2 acceleration phases. This is completely normal and a known fact. So this is not the stuttering you mean?
With buffer I meant this parameter:
/** \brief Number of moves we can cache in advance.
This number of moves can be cached in advance. If you want to cache more, increase this. Especially on
many very short moves the cache may go empty. The minimum value is 5.
*/
#define PRINTLINE_CACHE_SIZE 16