IP Passthrough intermittent

Hello,

We are trying to setup a basic IP Passthrough connection through a BR1 Mini.

Cellular Internet <–> BR1 (w/ Sprint static IP address) <–> Ubuntu Linux server

We setup IP Passthrough to the Linux box (through LAN connection), it is not getting the static IP address provided by Sprint.
When we connect another computer to the BR1 through the wireless, it picks up the static IP address.

Any suggestions on what I am missing?

Thanks!

Please ensure there is 1 LAN device only on the LAN side of BR1 Mini. If you still face the issue, please get help from your point of purchase.

Yes, there is only 1 LAN device. It eventually passes the IP to that device over the LAN, but it takes quite a bit of time. Like over 10-15 minutes.

While when a device is connected via wi-fi it seems to passthrough the IP right away.