If an account initiated the unbonding process from a pool before the Asset Hub migration, the UI gets confused and won't allow the user to withdraw those unbonded funds.
For example:
ESZAaeYCsAu46CQtyVH4Dbn1uaXSbgT2AnhgPv7yh98uDET (KRC and KAH)
The funds can be withdrawn if the corresponding extrinsic is issued.
Edit: This particular account's unbonding period is over, but the situation is similar to any other pool member. The locked balances or claimable rewards are not detected.