If the paths have differently sized devices, and could be distinguished in that way, then experimenting with a larger value for LVS PROPERTY RESOLUTION MAXIMUM may help. I think the default is 32. If the parallel branches can't be distinguished from one another based on device size properties, then that statement won't help.
Another approach that has helped in many situations is to make sure the ports/pins of the hcells are texted.
Experimenting with different HCELLS may be another possibility. Along those same lines would be to experiment by toggling your use of -automatch. That is, you may experiment by avoiding -automatch if you're using it already, or trying -automatch if you haven't already. Sometimes all it takes is to change the picture in some way, to allow Calibre to see things from a different perspective and then be able to work past a problem area.
If you don't find something that works, and if we don't get suggestions from other users, this may be a good candidate for opening an SR through Mentor SupportNet.
Let us know how it goes.