Sometimes bearings marketed as “stainless” is not always entirely stainless. Look at the inside part of the outer race, if it has a little rusty dust, it’s probably one I’m talking about, even if the outer part is completely shiny. The rust gathers around the ball bearing path increasing friction. It hasn’t happened to me somehow, unless the bearing is definitely not stainless… but my friends mostly have, for unknown reason.
Try to do paper slip method to clean the bearing, if the paper has rust in it when cleaning, unless you’re the “tinkerer” type, better save up for a new bearing.