Split tunnel and route list not working

Hello everybody, I have strange problem with 2 vpn clients, my company has a fortigate 201E. Employees connect through forticlient and split tunnel is enabled for a route list of internal network resources. All work fine for 20 people, 2 can connect but aren't able to resolve hosts name or fqdn name. This happend only when they connect trough their home ISP router although they are receiving correct DNS suffix and internal dns server. If they connect using tethering name resolution work fine. The difference I have notice is that during first option they aren't able to download the route list for internals  resource. The 2 OS client are windows 10. what can i do? Thanks in advance