Connectivity problem with LTE


I’ve a Turris Omnia where I’ve added a LTE Card with two 4G antennas.

With a french(Sosh/Orange) simcard -> Internet is working properly

When I use a Simcard from Bouygues (french provider also), I get an public IP, which I can ping from another internet connection.
On the LAN ports from the turris Omnia my clients get an IP and they can resolve DNS (they get IPv6 and IPv4 address), but traceroute and ping to outside does not work

I tried disabling IPv6 because my provider (Bouygues) is IPv4-only
(with this command in SSH Console)
echo “net.ipv6.conf.all.disable_ipv6=1” >> /etc/sysctl.conf

But my clients get still DNS answers with IPv6 and IPv4, and still no ping from the LAN side

Any idea what I can do to make this working ?