However, without any notification they have terminated their "legacy" accounts and converted them to "new" accounts with a 0 withdrawal limit. While I am just a hobbyist and don't have a lot of BTC I find this very upsetting and unprofessional to have done this without any notification.
Worse, when I tried to do a Basic Verification (which is all I really need) it failed instantly. This does not give a lot of confidence about their verification systems or service.
I did Basic Verification on a new account a few months back. They weren't able to verify my details through public records. But instead of rejecting the verification, they allowed me to simply verify my mobile phone number via SMS. Did they offer you this option, or is that gone too?
So if you don't have a verified account at Bittrex I would advise against depositing until you do.
I heard recently of multiple cases where people with "enhanced" verification still had their accounts disabled and reduced to "new" account status. Bittrex is definitely making lots of changes (KYC, disabling accounts, new minimum/stale order policies and supposed policies against "pump groups") and they've been doing so ever since BTC-e got shut down.
I can't tell if they are being directly pressured by regulators or law enforcement agencies, or if they are just scared and doing everything they can to more closely comply with existing regulations.