- what was previous ROS version where it worked?
- what is your current ROS version? (as pointed by @inteq, 6.48.3 does not exist and it will probably be 6.43.8. just making sure)
- what specific rule are you using? is it or ? (or any other?) Ideally just share whole .. It should be pretty clear where is the trouble. If you are worried about personal data, feel free to find+replace all occurences with some meaningful string.
My first guess would be some BC-break feature, typically hw-offloading which was not originally active, but now it is active and it prevents CPU to see bridged packets, therefore firwall ruless are completely avoided.