MoSh PPP working on nRF9161 but not on nRF9160

I have the MoSh sample running on a nRF9160 DK connected to a Ubuntu PC, and the goal is to get internet connectivity through PPP. While I'm able to startup a PPP connection between the PC and the modem, I cannot ping IP or domain addresses nor send or receive any data, and often times I cannot completely start the connection at all.

I thought the issue was poor service or bad configuration, but I'm able to get a functional PPP connection using the nRF9161 DK with good speeds and no issues starting and maintaining the connection.

Both DKs are running the same MoSh sample and are using the exact same SIM card.

Below are the outputs from the MoSh terminal and the pppd terminal on my PC.

nRF9160 output on a successful PPP connection:

MoSh output on the 9160pppd output on the 9160

Attempts to ping google only succeed sometimes, other times it fails:

nRF9160 output on a successful connection that fails shortly afterward:

nRF9161 output on a successful PPP connection:

MoSh output on the 9161

PPP connection script:

systemctl stop NetworkManager
echo "nameserver" > /etc/resolv.conf
pppd -detach /dev/ttyACM0 921600 noauth crtscts noccp novj nodeflate nobsdcomp local debug noipdefault defaultroute ipcp-restart 5 lcp-echo-interval 0 

On the 9161 I get speeds around 8 KB/s, while the nRF9160 will sometimes get around 200 B/s before stopping completely.

Is this expected? Is there a configuration issue I am missing? Any help would be appreciated.