Recognize App sorting is purely random

I am using the recognize app and find it really good.

At the beginning the sorting was OK and everyone was listed by the amount of photos. Now I reorganized the pictures in the external backend (SMB) and the order in the people tab is completly messed up, also whenI merge two people with one another, the persons to select is completely chaotic. It also changes after each reload.

Is it random?

I had two empty clusters and after I removed them, the sorting seems OK again, is this a bug?