The Pilgrims journeyed to Mill Farm to face AFC Fylde – and suffered a 3-1 reversal.
Rueben Fogg scored United's goal – with keeper Zach Marsh making a welcome return from injury.
Boston: Zach Marsh (Austin Barker 46), Oliver Nicholson (Oliver Callaby 85), Oliver Houlston, Charlie Brooks (Toby Cotton 80), Kirils Snikeris, Jake Thompson, Will Green, Harry Wood, Will Pettitt, Will Langford, Rueben Fogg (Dexter Tomlinson 70). Sub (not used): Rhys Smaller.