How To Put The New PMDT Headband Jiggles into my Build?

I would like to replace the headband puff that is currently in Psycho Ghost's build I have a build based off his, which I have added my own personal touches to.

When I try to put this Jiggles Headband in, the game will freeze and need to be restarted.

The problem is that the file I want to put it over is FitPurin02, the sleeping cap. Some how the creator managed to put his model swap in over the sleeping cap and made it function, but I cannot.

Any help is appreciated.