The call will always take the first VMID that was associated with the beginning of the call so in your case 5804 even if the call diverts to 5827 and then onto VM.

Are they able to do a call pickup from 5827 when they hear 5804 ringing?
If you have a Strata Messaging or IPedge voicemail then set a message cascade from mailbox 5804 to 5827 after 1 minute


Regards
Carl