Thanks for the topology.
You will need to separate the traffic from the cameras and your VDSL device using 10.0.0.138 into a different VLAN from your global default VLAN for traffic in the 192.168.240.254 VLAN.
Create the new VLAN on all switches that include cameras or the VDSL
Add the VLAN to the LAG connecting the switches
Assign the VLAN to all the ports where the camera and VDSL connect and remove the existing VLAN
This book has a good overview of the details.
See chapter 4 pages 56 - 61