Long time no see ^^
I saw that you couldn't, also saw your "bug report" about it ^^ I'll send my mail.
For your problem, please, upload a capx ^^
The problem is event 61. You think you picked the volume with the condition "NPC Is overlapping Volume" when in fact you picked both. You have to pick the NPC first.
If you don't, the overlapping condition will just pick the 2 NPCs and the 2 volumes (they are overlapping at first). Then, the NPC : Pick instance with UID will just restrict the picked NPC to the one you wanted. In the end, your "picking set" will be the 2 volumes and the NPC. I'm not sure what the function calling will send in Volume.UID, as there are 2. Not what you want anyway.
Next, you could easily just change the Find Path parameters to :
X : random(Volume.Width)+Volume.X
Y : random(Volume.Height)+Volume.Y
Making the NPC obligated to move inside the volume.
Last thing, event 62, the function picks a volume, but no NPC is specified, so all NPC are selected. You have to add a second parameter to the function (NPC.UID) and select the NPC too in the function event. You could also forget about the volume.UID, as with the PathFinding I suggested, you should be able to pick the volume with the same "NPC is overlapping Volume" condition in the end of event 62.