You're getting the UnusedValueWithoutDrop error because every object returned from a Move call must be either transferred, used, destroyed, or explicitly dropped — otherwise, Sui throws that error to ensure safe and deterministic object handling.

In your case, you’re handling returnCoinA and returnCoinB correctly by transferring them back to the sender. But you’re not doing anything with returnReceip, which is why the error is triggered.

To fix this, you should explicitly drop returnReceip if it’s not needed, or transfer it if it contains data the user should keep. Here's how you can handle it depending on the case:

✅ Option 1: Drop the object if you don’t need it

tx.moveCall({
  target: '0x2::object::drop',
  arguments: [returnReceip],
});

✅ Option 2: Transfer it to the sender if it holds useful info

tx.transferObjects([returnReceip], tx.pure.address(sender));

✅ Final fixed code:

let [returnCoinA, returnCoinB, returnReceip] = tx.moveCall({
    target: targetFunctionLP2,
    typeArguments: [suiTokenType, usdcTokenType],
    arguments: [
        tx.object(poolAddressLP2),
        tx.pure.bool(false),
        tx.pure.bool(true),
        tx.pure.u64(amountOutUSDNormalized),
        tx.pure.u128(limit_sqrt_priceB),
        tx.object(clockObjectAddressLP2),
        tx.object(versionAddressLP2),
    ],
});

tx.transferObjects([returnCoinA, returnCoinB], tx.pure.address(sender));
tx.moveCall({
  target: '0x2::object::drop',
  arguments: [returnReceip],
});

This will resolve the UnusedValueWithoutDrop error. You can also inspect the structure of returnReceip using devInspectTransactionBlock() to decide whether to drop or keep it.

🔗 Read more on object handling in Sui Move

You need to do something with returnReceipt. I don't know what these objects are, but you can probably just add them to transferObjects if they aren't expected to be passed into another call