Queue Members showing Ring No Answer while on other calls

We have several members who all are part of multiple queues. Users are showing a high volume of ring no answers. We have shut off call waiting for the extensions and on the Yealink phones themselves. We traced a call that showed as a ring no answer and was able to see that the agent was already on a call.
We also believe this is affecting our hold times as a call will sit in queue waiting for this person for long periods.