I was reading on reddit not too long ago about the problems with poloniex. I haven't set up an account over there because I've been sort of leery about sending them my SBD or Steem.
I think this has most likely been an ongoing problem for a while if so many people are discussing it, and that thread on reddit can be found here:
Here's so more info that might be helpful - https://themerkle.com/poloniex-solves-70000-account-balance-issue-after-reddit-complaint/