render problem with multi-type objects as one geo node

[tagosaku 3]

Hi, I have a problem to render Mantra with multi object type. Whening clicking render button from render view, it shows messages, 'generating scene' and 'Rendering(0.0%)'. However, actual rendering won't start. I am guessing problems are I try to merge different types of geos and render it as one Geo object. Is that really problem for Mantra????  here is test details;

1 - there are polygon, packed Geos, packed fragment, and (polysoup if unpacking ).  Of course, NOT merging volumes

2 - This problem happens with turning on motion blur in Mantra. There is no problem with motion blur OFF.

3 - Mantra render's motion blur is ON, and delete attribute v (and w). Then rendering is working.

4 - surprisingly when changing order of merge-lines, rendering works somehow sometimes., strange !!

Thus, I have not found logic to fail render mantra. If you have similar issue and solution, let me know, thanks!