Brake Booster Failure

Has anyone had to replace the Intelligent Brake Control Unit (Brake Booster) in a 2016 Nissan Leaf. All brake warning lights are on and brakes go completely to the floor with grinding sounds. Dealership wants $3700 for a new unit and warranty has expired. New 12v battery and tried to clear DTC's with LeafSpy, but no luck. Been to several repair shops, but once you mention the words "Electric Car", you're basically speaking a foreign language and they have been no help. I'm wondering if anyone on here has actually purchased a used Brake Booster from Ebay or a junkyard and then installed it. Any comments would be greatly appreciated.

I had to have the intelligent brake controller replaced (under extended warranty) on my 2015 and under Nissan warranty on my 2019. The brakes still functioned in both cases, but there was a loud pulsating/grinding noise and the pedal went closer to the floor before brakes would apply. The controllers became intermittent and I could clear the DTC's with LEAF Spy Pro to restore normal operation for a while. Clearing DTC's generally required several iterations of clearing with LEAF Spy, disconnecting 12V battery, reconnecting 12V battery, and clearing DTC's with LEAF Spy. I eventually got tired of having to periodically clear codes on the 2015 so I took it to the dealer. The aftermarket warranty company baulked at the repair cost and tried to find a used module before finally agreeing to the repair. I did not care how long they argued because they were paying for a rental car while my car was in the shop. The 2019 eventually got to the point where the failure was no longer intermittent at a little under 60,000 miles so it was under the Nissan EV System warranty. There was no argument, but it took a while to get the part. The technician and service advisor confirmed that the car was safe to drive so I ended up driving with it that way for a week or two. The 2015 had no more issues after replacement until I traded it for the 2019. The 2019 has been fine since the replacement.