Brand Registry was primarily built to protect brand owners against counterfeit sellers infringing on their copyrights, trademarks, and patents. If counterfeit sellers are causing price erosion then Brand Registry can be an effective tool to protect pricing.
However, if the MAP violations are coming from sellers with your authentic products then Brand Registry will not be very helpful. Brand Registry violations mentioning MAP pricing violations will get rejected, often stating that it is the brand’s responsibility to police their distribution, not Amazon’s.