ReadyNAS 4312X SMB shares intermittently hang/freeze

Further information:
When the connection drops, it's down for five or ten seconds for all clients at the same time.  If a client isn't actively trying to read or write to the share, they don't even notice.

Date and time are configured to time-sync to the DCs and match.

There are no other apps on the device; NFS and Rsync are enabled for support of some backup jobs, but almost completely unused.

Audit logs are turned on, but the information in them consists solely of the login/logoff which doesn't seem to correlate with the drops.

This network configuration has existed longer than the trouble with the dropping share has occurred, but might still somehow be relevant:
Bond0 is running subinterfaces for access segmentation and service control.  
bond0: (native VLAN 6), IP address 192.168.6.X/255.255.255.0/192.168.6.1  DNS nas1.sec.domain.local
bond0.2: (trunk VLAN 2) IP address 192.168.2.X/255.255.255.0/192.168.2.1   DNS nas1.domain.local

bond0.7: (trunk VLAN 7) IP address 192.168.7.X/255.255.255.0/192.168.7.1   DNS nas1.dev.domain.local

SSH/HTTPS/etc. are access-list blocked at the switches for all but VLAN 6, and you can only reach that VLAN through a firewalled management portal.