This is quite a common problem as I understand from my own candidates.
Unless it's a technical issue involved, then it has to do with the reliability of some practice partners.
Some people just don't show up for peer meetings and that can get really frustrating, especially when you spend time scheduling these meetings and planning around them.
My recommendation in the prep process is always to look for 1-3 reliable partners that prepare their cases and give granular feedback and work with each other in a smaller practice pod.
Best,
Cristian