Hello,
From what I read, someone who sells btc sometimes has trouble receiving the fiats in its bank account. If the sum is large, the bank turns on all its red lights. I guess it's not a problem for someone famous, but for an ordinary citizen, how it happens if he lives modestly, recovers his private keys that he lost 10 years ago and finds himself with millions?
In country if a huge amount of money is received, then the banks are going to freeze your account which you will be invited to defend the source of the money, but if scenario like this can happen, all what I will do is converting my bitcoin to fiat gradually, since all accounts in my country is having limit, if you haven't exceeded the limit, then they wont be able to freeze your account, I will make sure i don't go beyond my limit, after spend the money I withdraw in my account, then i will convert another bitcoin to fiat. If you can be doing it like that the banks wont be able to do anything with your account, but immediately you withdraw everything at once, then you will have to visit the bank and explain your source of income, and in my country the central bank have given all other commercial banks the permission to ban all accounts that are connected to crypt currency activities.