Pen Tool Spiro path sometimes creates a segment instead of a curve.

Summary:

When using the Pen Tool in" Spiro path" mode, some of the curves are transformed into straight lines.

Notes:

1. I noticed the same behavior on Windows 10, and on KUbuntu 22.04 for Inkscape 1.4.
2. It seems similar to the following report, even thought this report only mentions this for the first part of the curve, and I noticed that it now happens for any part of the curve: inkscape#4734

Steps to reproduce:

• open Inkscape
• Select "Pen Tool"
• Select "Create Spiro path"
• Create a small curve (length less than 3 mm for instance)
• Sometimes, the curve that is displayed is transformed into a straight line.

What happened?

• The curve is not a curve anymore: its is a straight line.

What should have happened?

• The curve should have remained a curve.

Sample attachments:

Version info

Inkscape 1.4 (86a8ad7, 2024-10-11)

                      Compile  (Run)
    GLib version:     2.82.1
    GTK version:      3.24.43 (3.24.43)
    glibmm version:   2.66.7
    gtkmm version:    3.24.9
    libxml2 version:  2.12.9
    libxslt version:  1.1.42
    Cairo version:    1.18.2 (1.18.2)
    Pango version:    1.54.0 (1.54.0)
    HarfBuzz version: 10.0.1 (10.0.1)

    OS version:       Windows 10 22H2