AFAICT not related to the number of objects inside a group but to Inkscape's interpretation of the path data ('A' in particular), see attached version of the sample file.
Inkscape doesn't visible render:
<path d="M 84.6638,42.9675 A -86.8990,-86.8990 0 0 0 91.1528,64.7048"/>
but does render this ok:
<path d="M 84.6638,42.9675 A 86.8990,86.8990 0 0 0 91.1528,64.7048"/>
AFAICT not related to the number of objects inside a group but to Inkscape's interpretation of the path data ('A' in particular), see attached version of the sample file.
Inkscape doesn't visible render:
<path d="M 84.6638,42.9675 A -86.8990,-86.8990 0 0 0 91.1528,64.7048"/>
but does render this ok:
<path d="M 84.6638,42.9675 A 86.8990,86.8990 0 0 0 91.1528,64.7048"/>