Problem with the "initializing" state on a TP-LINK Mesh HC220-g5: What does the device do during the initializing state?

(The manual indicates that this state is shown by a flashing yellow LED.)

Why do my devices take so long (20/30/60 minutes) to initialize?

Context: My devices have been reset to factory settings and are not associated with any network. When turned on, they take between 20 and 30 minutes to get past this state. However, when moved to another location, they get past the state in just 2 minutes. Any idea why?