Drew the following: 5 POLYLINEs, 2 SPLINEs, 5 LINEs.

Used the command EDITPOLYLINE>SPLINE on some of the POLYLINEs and they were transformed into Type: 2D POLYLINEs.

TRIM command used and had no problems with POLYLINEs and SPLINEs, but 2D POLYLINEs behaved strangely:

1. Always the first use of TRIM on them, the command will not work correctly.
2. The pieces that remain are 2D POLYLINEs and has no problem with TRIM. But the new 2D POLYLINE objects have changed - they are composed of many straight lines that are close to the first spline form. If still need to be smoothed then have to be used EDITPOLYLINE>SPLINE again.

If apply EDITPOLYLINE>DECURVE, objects are transformed from Type 2D POLYLINE in Type POLYLINE.

P.S. DraftSight V1R1.4

P.S.2 (2012-04-12) Second attempt - the same video, less in size, but very poor quality.