The bot doesn't require that much memory, but it's possible that bundler needs a bit more in the beginning. Maybe you can enable a temporary swap to get it to bundle:
sudo dd if=/dev/zero of=/var/swap.img bs=1024k count=4000
sudo chmod 600 /var/swap.img
sudo mkswap /var/swap.img
sudo swapon /var/swap.img
Thank you very much for the quick answer. I have made the suggested steps but the same problem persists.