Have there been any issues in recent times, say going back to the previous 12 months?
Recent issues with Bittrex are Two Types.
IEO: They listed IEO's Which had bad reputation in the past. But the team members from the IEO's are too close to Bittrex Core Team Members. Such a bad price & all the Team members from these IEO projects dumped their bags and as a result, Bittrex lost more customers. If you check Bittrex has only a few Coins that have a volume over 100
BTC.This indicates that Bittrex is falling so hard. Bittrex is the only exchange none of their IEO's were successful.
Token Listing: Token listing policy of Bittrex changed a lot. If you have a good whitepaper and a team with lot of money and connection with Bittex CEO You can list your tokens easily. In the past, we saw Bittrex listing policy was great. That caused them losing customers as well.
Though I know that we're in a bear market as well. IEO's price 40% down in the first hour is fishy.
To be honest if those two are the only reasons users might be concerned or put off from using Bittrex then I see no problem at all if the objective is to send your crypto there, have a trade then withdraw the exchanged crypto back to your desktop wallet.