Welcome!
Get yourself a good pair of medical grade tweezers if you don't already have them, and use them for placing the wires in the mold. I also use a wood dowel, that had been sharpened on one end in a pencil sharpener, to nudge wires & hooks when necessary. The wood, unlike metal tools, won't become magnetic, so the wires & hooks won't stick to it.
As others have indicated, having everything seated in the grooves is necessary.
I actually gave up on using the WB400 wires, and have modified my molds for the larger WB800. My issue was primarily that the smaller wires too easily became loose, especially in heads that were smaller, like in the Midwest Finesse mold.
Unfortunately, the WB800 wires are longer than needed for some molds and that mean I have to spend the time cutting or bending them to fit. I'm not going back to the WB400, as I'll do the extra effort to pour heads that I don't get loose keep wires.
