addLiquidity() function reverts without any reason on local development instance of ganache, any ideas why this might be happening?

Some background:

• I have forked the UniswapV2Factory and UniswapV2Router02 and deployed on ganache.
• I have created 2 ERC20 tokens, and created a pair (via factory.createPair()) for them.
• Minted both ERC20 tokens to my address.
• I have approved token amounts to the router contract address (via erc20.approve() function)

This is how I am calling the addLiquidity Function

const blockNumber = await web3.eth.getBlockNumber();
const block = await web3.eth.getBlock(blockNumber);
const timestamp = block.timestamp + 300;

await router.addLiquidity(
    ERC20_TOKEN_1_ADDRESS,
    ERC20_TOKEN_2_ADDRESS,
    web3.utils.toWei('1', 'ether'),
    web3.utils.toWei('1', 'ether'),
    web3.utils.toWei('0.001', 'ether'),
    web3.utils.toWei('0.001', 'ether'),
    OWNER_ADDRESS,
    timestamp,
    { gas: 4000000 }
)