Issue with RDP over VPN to Terminal Server

Remote office accesses main site via site to site VPN (sonicwall soho to a TZ400).

There is one user at the remote site accessing a terminal server back at the main site via RDP. The issue

started last week when they were suddenly kicked off their session and unable to reconnect. I am unable to ping

the terminal server after being disconnected, but am able to ping other servers on the same subnet as the TS.

I am also able to ping from the terminal server to the LAN gateway of the remote site firewall, but not the

PC. I have checked the Windows firewall logs and disabled the AV on both the server and workstation and still

not able to RDP in. The computer at the remote site is receiving it's IP address via DHCP from the sonicwall.

I terminated the lease for the workstation, reduced the size of the pool so it received a new address and did

a /release and /renew and voila! With a new IP address the computer was able to RDP to the terminal server

again. Chalk that up to a weird one time issue right? Nope, 3 days later the same issue is occuring, after no

issues within that 3 days. I applied the same bandaid and it worked like a charm. Has anyone ever seen an

issue like this, or have any ideas as to why this is happening? If more information is needed, please

let me know.