What sized nest. especially width and height? What sized chickens? What does the nest look like?
I have had full-sized hens use an entry hole that was 6" high and 8" wide. The lip wasn't originally high enough to keep the bedding and eggs from being scratched out so I had to raise the lip which shrunk the opening.
The size of your nest may limit it. You need enough of a lip across the bottom to hold stuff in. After my bad experience I now use about a 4" high lip. Many people use less and do OK. If your nest isn't very tall that may not leave much room for the opening. The nests I have now are 16" high so I have plenty of room and use an 8" x 8" opening.
Chickens like things to stay the same, any change can throw them off.
Keeping them in a tractor can break the habit of coop nest laying.
It could take a good long while to get them used to laying in either the coop or the tractor.