FortiClient macOS client fails to connect when specific USB keyboard attached

So this is weird one. I use FortiClient on my Mac to connect to a client's corporate network. Recently, I'd been unable to establish a VPN connection via FortiClient in my office, but I could connect at home using the same laptop. After much troubleshooting, it turns out that when the keyboard I use in the office is connected to my Macbook FortiClient can not establish the VPN connection.

It's not if any keyboard is connected, but specifically this one from Monoprice, https://www.monoprice.com/product?c_id=114&cp_id=11401&cs_id=1140102&p_id=12515&seq=1&format=2

I've been able to reproduce the issue consistently. My workaround is to just unplug the keyboard, connect to the VPN, and then re-connect the keyboard. FortiClient remains connected all day even with the problem keyboard plugged back in after establishing the VPN connection.

I have a 2015 Macbook Pro 15", running macOS Sierra 10.12.6 and FortiClient 5.6.0.703 installed.

Has anyone encountered anything like this before? A bug in the Mac client? Maybe something more nefarious about this keyboard?