If you use random words to generate a mnemonic seed and some of them are not from those BIP words list, you may end up in having an invalid wallet seed.

NEVER start a new wallet seed with words that YOU choose. The probability that somebody else use them too is higher the the entropy of a wallet app.

bitcoin_beginners

Is it possible to use a custom word list to generate Bitcoin seed phrases?

0xbitcoiner

If you use random words to generate a mnemonic seed and some of them are not from those BIP words list, you may end up in having an invalid wallet seed.

NEVER start a new wallet seed with words that YOU choose. The probability that somebody else use them too is higher the the entropy of a wallet app.

*is a good question btw*