FortiClient 6.0.4.0182 saving file to network location stalled/blocked

We are experiencing an issue where saving a Word document to a network share (DFS) is stalled/blocked. After 1 minute the operation gets cancelled. Word saves a temp. file but does not get to rename it to its final destination.

This seems to be induced by having another security product also. It's hanging inside fortimon3.sys (with timeout)  on a call on which it should not hang. We can provide a stack trace if needed. Public symbols for the driver would of course be very helpful.

Realtime Protection is on

Dynamic Threat Detection is on

AntiExploit is off

Sandbox Detection is off