Why does my product category keep reverting to manual sorting?

[Charlievdm]

I would like to set my product category to 'Best Selling', but I noticed that it keeps changing back to 'Manual' sorting every time I log back in. This happens both on shopify as well as on the website itself. 

Is there something I am missing? Why does it keep automatically switching back? Thanks!

[Chickenoriental]

Did you ever get an answer for this? It's highly irritating