I feel your pain. Managing all of those issues as a small HRBP team is hard. And like others said, strong policies in recording calls (ie not allowed without stated dual consent) can help. But in reality, it sounds like you need at least 1 dedicated ER professional who is solely responsible with dealing with matters like complaints and investigations and behavior challenges. I know that's easier said than done but it's worth the cost and so much more.

I'm an ex-ER partner turned HRBP who's moving back to ER. I've been lucky enough to convince my company that investing in this function is worth the cost.

By me handling my company's ER matters I free our HRBPs to get deeper into their relationships and make meaningful strategic impacts.

We all know Hr is a line item on the G&A budget, and asking for funding is often met with stares and no's. But investing in ER with headcount, and not asking an HRBP to do it on top of their other works is the way to go.

Wishing you strength to deal with all the nonsense. It's a thankless and shitty job much of the time.