FortiClient Split-Tunnel Sometimes DNS Queries to On-Prem Stop Working

I have had two or three new reports of users running FortiClient 7.0.6 and who report they suddenly can't get to resources over their SSLVPN. The problem is that name lookups stop working. I can ping the resources over the tunnel, but nslookup reports no such host - even though it's querying the correct name servers. Sometimes restarting the tunnel works, for a while. I have not had a chance to start looking at logs, but I'm wondering if this behavior will even get recorded in a FortiClient log.

Anyone else run across this behavior? TIA.