Don't panic, the new Borderlands 4 update's boss farming nerf was an accident and Gearbox is reversing it.
A recent Borderlands 4 patch caused the skill cooldown reset from vendors to stop working.
A Gearbox dev says it wasn't intentional.
The patch notes are largely focused on dealing with some of the "unintended interactions" that were leading to ludicrous damage scaling and boss-melting builds.
One of the best ways to farm for Borderlands 4 legendary weapons is repeatedly fighting a given boss over and over.
Author's summary: Gearbox reverses Borderlands 4 update nerf.