Q: Bluetooth not deleting old devices

I have just taken possession of a fully reconditioned MacBook pro and I find a lot of devices listed in Bluetooth that are no longer connected to this Mac. I've gone into System preferences and within Bluetooth preferences, tried hitting the 'x' next to the listing but it only then tries to re-pair the devices, which it can't do. I've also tried holding down the control key, the alt key and any variation of the Vulcan Death Grip Cmd/alt/Shift. Meanwhile it steadfastly refuses to pair (even though it is discoverable) my main iMac. I suspect this is a bug as there are other recent posts about it, so Apple, please address it.