I sent approx. 0.3. BTC to this wallet. All fine.
Backed up the seed and made a walet.aes.json file and backed that up too.
any chance you remember the address you used to send or receive that amount? check your email, exchange account and etc
even a txid could shed some light, so that you can trace and check its balance on block explorer
just shooting in the dark, it could be a simple uncompressed/compressed private key problem
I've seen this before when bc.info wallet is displaying a compressed key for an uncompressed (legacy) address