In the following example I want the hairpin to show that the first two notes have a diminuendo, but the third note should be at the same dynamic as the second (see the 1st line). In the first line when space is short the hairpin continues to the next note. It works OK in the 1st line where there's enough space, or in the 3rd line when the second note has its own dynamic.
The problem seems to be that the end of the hairpin is aligned to the right-hand side of the notehead, rather than the stem, and there isn't enough room between the notes to show exactly where the composer wants the hairpin to end. Overriding Hairpin.minimum-length doesn't change this.
A workaround (thanks to Phil Holmes) is to add -\hide\p to the second note.