See the issue I reported to Better Combat here:
ZsoltMolnarrr/BetterCombat#472

If the player is holding the Soulrender in their primary hand and any non-weapon item in their offhand, no attacks will be considered valid and the client will crash.

I submitted the issue to Better Combat as I feel they should probably handle this more gracefully than crashing.

Still, it seems like the Soulrender's weapon attributes probably need another look; not sure what the intent is for them.

Thanks for the report, Muon!
I'm aware of this one and forgot to fix it in the last update. I'll resolve it next update 🙂

This is fixed in the latest release 🙂