The issue is in the iimplementation of the TCP stack within FreeBSD on Data ONTAP. It affects the response time of ZAPI calls (such as from SnapDrive), due to the way that FreeBSD inserts wait packets into a TCP request.
There is currently a workaround available for these, so I suggest contacting NetApp Support for assistance in applying this. The workaround entails modifying one of the running parameters within ONATP, so it should be done in conjuction with a NetApp engineer.
When creating the case(s), please ensure you open the case as a SnapDrive/SnapManager case so it is routed to the group with the right experience for dealing with this issue.