RDP through VPN issue - Unsure if VPN or RDP dropping 1st

Hi,

My wife has a Toshiba Satellite P55T-B laptop running Windows 8.1. The laptop connects to our router - an Asus RT-AC87R - via wifi. The router is running the latest firmware. The NIC drivers on the laptop have are also running the latest driver version.

My wife remotely connects to a desktop machine setup for her at work. That machine is always on and set to wake on WAN connections. She RDPs through a SonicWall IPSec VPN peer connection. She's experiencing a few problems.

1) RDP will intermittently attempt to reestablish connection.
2) The VPN will eventually sever the entire connection.
3) The VPN connection drop will affect the entire laptop's connection to the internet.

So, I'm not sure if the issue lies with my home router, with the VPN, or with the RDP.

I looked at her RDP settings, and they seem configured correctly, with automatic reconnect attempts, etc.

I looked at her VPN settings, and the peer's IP address is correct. When there's a disconnect, RDP will report an error that it couldn't find her machine, which is odd because it was just connected to it. (I believe the VPN connection is a tunnel right into her desktop at work, rather than into the corporate network.)
I looked at my router, disabled a number of settings (e.g., firewall, explicit/implicit beam forming, 2.4ghz and 5ghz band setting, etc.) to no avail.

I'm totally stumped. I'm not sure why her connection drops. I can't tell if it's the RDP connection, the VPN connection, or my router.

I'd REALLY appreciate some help.

Thanks,
Julian