Cannot connect AC1900 as wireless client

Background

I have an existing Linksys Velop mesh network and and older Linksys WRT AC1900. I tried using the AC1900 as a wireless bridge using the factory firmware and the upload speeds were terrible, so I decided to flash it and follow https://openwrt.org/docs/guide-user/network/wifi/relay_configuration.

The Problem

When configuring radio0 the wifi never seems to fully connect, and while I see reasonable TX and RX rates the Encryption on the connection is shown as "-". I've tired changing the encryption mode on the 5GHz band from the Velop side of things, because I've already read that the Marvell antennas may have some issues there, and tired using WPA2-PSK (forced CCMP), and that didn't change anything. It seems regardless of what I do or change I am unable to get a proper wireless connection.

Is there a workaround I'm missing?