Some people have noticed that when transferring tokens between their own accounts, they have to sign for both the "withdrawing from" account and the "depositing to" account. This is especially noticeable when both of those accounts use Ledger hardware wallets, but it actually is the case for all accounts.
This is not a bug! One of the reasons they are called "smart accounts" on Radix’s Babylon mainnet is that they can have rules applied to them. You've probably noticed that you can configure some "third party deposit rules" to your accounts through the Radix Wallet. Those rules let you block other people from depositing some assets to your account, if you wish. But what this means is that the account has to know if a deposit is coming from its owner or somebody else to decide if the deposit is allowed or not. That's why you have to sign for the "depositing to" account – that's just you identifying yourself to your account.
However, an optimization is planned. The wallet can be intelligent about looking at the account settings and figuring out if a deposit would actually be blocked or not before asking for the extra signature. If you have third party deposits turned off, you would still have to sign. Otherwise, no need. This improvement is on the list of items to implement in the Radix Wallet in the near future.