After generating a 2-out-of-3 wallet (using brainwallet http://ms-brainwallet.org/#generator) I am able to store my private/public keys for each of the participants.
Afterwards I send a small amount of BTC to this address (0.0002). The amount is correctly recorded and confirmed in the blockchain and is listed as an unspent transaction.
Afterwards I create a new transaction that spends (0.0001 BTC). This transaction is successful. On the third step I sent more funds to the 2-out-of-3 wallet (0.0003). This is where the issue happens: any funds I deposit in this wallet from second transaction on are automatically spent towards various unknown addresses, and there is never any unspent transactions no matter how much I deposit there.
I have tested this with several wallets already.
What I am thinking of is that there is a change problem. I found some ways that funds can 'evaporate' but I haven't been able to nail the issue completely. Any inputs would be appreciated.