How many batches have you made using this process before it started happening?
My guess is you have a bit of gunk stuck somewhere in your spigot, hose, bottling wand, or autosiphon. I know I have had some crud inside each of those before that was basically impossible to get out just by normal cleaning and sanitizing procedures.
Look VERY CLOSELY at each one for spots and what have you. Especially the spigot...those can get mold & bacteria forming in the ring between the outer and inner sections of the valve that you sometimes cannot even see without taking it apart.
The timing certainly suggests the infection is being introduced as part of the bottling process.
My guess is you have a bit of gunk stuck somewhere in your spigot, hose, bottling wand, or autosiphon. I know I have had some crud inside each of those before that was basically impossible to get out just by normal cleaning and sanitizing procedures.
Look VERY CLOSELY at each one for spots and what have you. Especially the spigot...those can get mold & bacteria forming in the ring between the outer and inner sections of the valve that you sometimes cannot even see without taking it apart.
The timing certainly suggests the infection is being introduced as part of the bottling process.