A user reported to me that they are unable to create a PSBT with a legacy watchonly wallet when they use the GUI. They get an error "The amount exceeds your balance".

I think the issue is that the GUI will retrieve the wallet's balance via `AvailableCoins` before calling `CreateTransaction`. This call to `AvailableCoins` is resulting in fewer coins being returned with recent changes to how `AvailableCoins` works, particularly with additional filtering of spendable coins and preset coins.

***

Note that this does not effect descriptor wallets. A workaround for this issue is to switch to using descriptor wallets. An existing legacy wallet can be turned into a descriptor wallet using the `migratewallet` RPC. However many watchonly legacy wallets are likely the result of importing descriptors via `importmulti`. For such wallets, I recommend creating a new descriptor wallet and re-importing the descriptors.
result.is_coinbase = wtx.IsCoinBase();
    result.is_in_main_chain = wallet.IsTxInMainChain(wtx);
    return result;
}
WalletTxOut MakeWalletTxOut(const CWallet& wallet,
    const CWalletTx& wtx,
    int n,
    int depth) EXCLUSIVE_LOCKS_REQUIRED(wallet.cs_wallet)
{
    WalletTxOut result;
    result.txout = wtx.tx->vout[n];
    result.time = wtx.GetTxTime();
    result.depth_in_main_chain = depth;
    result.is_spent = wallet.IsSpent(COutPoint(wtx.GetHash(), n));
    return result;
}
WalletTxOut MakeWalletTxOut(const CWallet& wallet,
    const COutput& output) EXCLUSIVE_LOCKS_REQUIRED(wallet.cs_wallet)
{
    WalletTxOut result;
    result.txout = output.txout;
    result.time = output.time;
    result.depth_in_main_chain = output.depth;
    result.is_spent = wallet.IsSpent(output.outpoint);
    return result;
}
class WalletImpl : public Wallet
{
public:
    explicit WalletImpl(WalletContext& context, const std::shared_ptr<CWallet>& wallet) : m_context(context), m_wallet(wallet) {}