The Pilgrims were beaten 3-0 by Mansfield Town Brooksby after shipping all three goals before half-time.
The result left the Pilgrims fifth in the standings prior to Christmas, five points off top spot and having played a game more than leaders Football CV Reds.
Boston (4-2-3-1): Oliver Swaby; Marshall Young, Callum Rodger, Jack Withers, Jack Brown; Taylor Gray, Peter Evison; Jamie Gaukroger (Jenson Ball 46), Jordan Tate, Leighton Boughen; Jenson Bark (Harrison Holland 55). Subs (not used): Ryan Pratt, Seth Greeves (gk).