Readyshare unstable/disconnects drive when in use for 2-3 minutes (RAX54v2)

Running V1.1.4.28_2.1.26 version on RAX54v2.  WiFi is rock solid.  My router settings are pretty vanilla. Have a single drive hooked up to the USB port.

Readyshare sees the drive, shows all the files, I can read and write data no problem.

But if I use Readyshare with an application that needs to read and write for longish periods (e.g., music player), the shared drive disappears/stops functioning for a second or two every 3-5 minutes.  Screws up applications, results in partial file rewrites.
Nothing very interesting in the logs, except maybe when DHCP or NTP have something to do, it's coincident with the temporary drive disappearance.
Anybody else seeing this?