... what should i be looking for?
Do you mean an indication that it no longer works?
Aggression is one sign, some breeds are fine, I've had Araucana groups (at only 4-6 weeks) where the chicks who couldn't get clear of the over the top feisty ones had to be rescued to another brooder. Little buggers. Worse than quail.
Or if they are mixed breeds, the smaller ones can be squished by the larger ones even at a young age. They can self-destruct by burrowing into the centre of the group. And get pushed away from feed/water by 'everyone else'.
But if you meant you are looking for a short-term, crow-proof enclosure for a bit of time out from the box - if it doesn't need to be Fort Knox dog and fox proof, five pieces of lattice screening from Bunnings is fairly quick and easy. That's two long sides, two short ends, and a top the same size as the long-side pieces. Then cut shade-cloth to size and staple onto the lattice, makes it beak-proof. Instead of shade cloth, even netting curtain from an op-shop is cheap and works.
It's only a day-time transition between moving to secure grower pens - but I think netted lattice panels are under-rated as lightweight useful temporary barriers, in or out of pens.