I'm trying to send some ETH to a presale smart contract on Kovan. Allowance has been set with presale address as a spender - with the exact same amount as the tokens allocated in the presale contract. But then I got:
Warning! Error encountered during contract execution [Bad instruction] at tx hash: https://kovan.etherscan.io/tx/0x8d0451f2a9ba2440bf5f2a27d171850437772ccb12afeb8846507c0497e65cc0
From what I've read and learned, there's something wrong during the token transfer. But I can't find which one it is.
Would like to know if there's a way to fix this issue or at least knowing which one caused this, in case I'm facing the same issue in the future. Thanks.