I have tried sending 0.06 Ether to a contract as follows:

eth.sendTransaction({from: eth.accounts[0], to: "0x76E15697E36a66BF977D35de3C488F10B8014e65", value: web3.toWei(0.06, "ether")})

I've also tried sending 0.03 to the same contract address via MetaMask. However, although sending ether via eth.sendTransaction() through the geth command line submits, and on Etherscan no problems are shown, it doesn't add to a contract balance or trigger the fallback function (unlike sending Ether through MetaMask).

The contract in question is https://rinkeby.etherscan.io/address/0x76e15697e36a66bf977d35de3c488f10b8014e65

I'm trying this on the Rinkeby test network (not sure if it's a bug with this).