My only concern with your situation is that you described a noise with this issue. If that noise is mecanical in origin, then there may be physical damage to the trans internals. Valvebody malfunctions generally do not produce noise, but do cause function issues.
You can purchase a new “service level” valve body from Nissan or online parts stores for about $500 and slap it onto your trans easy enough. The TCU may still need the latest revision flash from the dealer, to work exactly like a factory new trans.
So, you could go through all this process above and still have an internal mechanical issue, and have basically not fixed the car.
Tough situation..
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