Poor file transfer performance from container, recent change

I run numerous containers on a single docker instance, a few of which have the need to move files around between local and remove file systems that are mounted on the host as CIFS devices, then presented to the container as volumes. In the past I haven’t had an issue when transferring data between these volumes, however recently I’ve seen the performance drop and transfer rates only running at less than 10 MByte/s when they used to run at around 60 MByte/s.

What are some things I can check in the configuration of either the docker engine on my server, or the container configuration?

I using the docker-ce package on Centos 7 for these containers.