Without pictures I?m not sure I fully understand your description. I was taught, by placing bees in a container, box, nuc, or full frame without ventilation, such a swarm or cutout, the bees may be dead before you can get home. 🤷🏻♂️
What I do when I move a Nuc, just for precaution, is this, I?ll use either door screen or number eight hardware cloth on the full bottom entry, (for ventilation ), cut a piece out to fit, then I will place this screen in position and staple it in place with T-50 staples. Then add the ratchet strap, or I will staple the top and bottom to the box. This has always worked for me.
I will add; Before I transfer a nuc into a full 10 frame box, I will first release the nuc in its new location for a day or two, usually 2 , giving them plenty of time to orient and get use to their new location and surroundings, letting them settle in, then transfer. This works well for me.
Phillip