They can be quite goofy about laying.
I have 3 boxes, each one gets used. One of my BO girls hogs the middle one, she is quite demanding when there is a need to lay her egg.
I do have a SLW who is a quite a Nervous Nellie and she absolutely refuses to lay in a box. Nothing I have tried works...
Can you put the kennel inside the run with the rest of the flock?
Not sure if it's large enough for 2 girls, you will have to determine that.
Atleast put the worst one in the cage, in the run, with her own food and water. I had a girl injure her foot and separated her for a few days, to keep her...