WRT1200AC USB File Sharing Instability. Thoughts?

[Anotherusername]

Hello- This is a hard problem to describe, but here goes:

Problem Description:
- Mapped drive within Windows 7 and 10 that is mapped from the WRT1200AC's usb drive sharing option becomes unstable and/or dropps connection.

Further Details
When I have my 5 computers connected to a file shared USB 3 memory stick (64GB) via a mapped drive (z, some machine's connections become unstable. Unstable means very very long time trying to open the maped drive (that is already open) or windows report that it is unable to connect the drive. Yet, another machine can connect fine and/or if I add another machine to the network, it can connect ok.

Setup:
- Shared USB 3 64BG Samsung Memory stick formatted NTFS
- Guest access is enables/all users can connect.
- Latest firmware on WRT1200AC
- Windows 7 and 10 machines are mostly up to date or very current
- Tried both 2Ghz and 5Ghz frequencies
- All the machines are in the same room within about 10-20ft of the router
- The router is NOT connected to the internet/LAN and no other router is connected to this network
- Utilizing IP to connect via Shared drive within windows by entering \\192.168.x.x, etc...

Anyone have any suggestions, seen this, or anything additional information I can supply?

Thank you in advance for the help!