Access Point channel fly issue

I’m in training and there is a topic on AP channel fly issue. can someone elaborate on the given topic. Also there is the topic of cpe been migrated to other ap types like T301 and ZF2741. like we have to check if the cpe is been migrated or not when cpe is not connected and we have to solve the issue.
So i think that channel fly issue and cpe migrating issue is somehow related? Can someone guide me through this.