If it runs twice at the first search the setupCallback of the rows seem to be called twice somehow.
I don't know why. Maybe due to other addons? Disable all other addons and try if it's still called twice.
Oh and remove this from your code as the stable scene won't be active for the guild store at all
It was the example for the normal inventory which gets called if you buy more inventory space at the stable master.
Lua Code:
--Do not execute if horse is changed
if SCENE_MANAGER:GetCurrentScene() ~= STABLES_SCENE then
-- Do your stuff here
end