I am not familiar with those error messages you are seeing.
My normal approach to debugging things like that would be to go and look in the /usr/lib/firewall/rules.pl code at lines 392 and 394 and see where the variable $source is coming from and try and figure out how it has ended up uninitialized.
It might be related to the following error lines where it has “-d none” towards the right hand side of your screenshot. That is saying that your forward rule has a source of 10.10.2.4 and a destination of none which is definitely incorrect.
Maybe when you have reconfigured your network cards you have changed the address of one of them and that has caused an existing firewall rule to end up with a destination of none.
The above is just guesswork on my part but would be how I would be trying to debug the problem.
I do not understand the section titled # Prepare source options. I don’t know what file that would be in or what it is doing so can’t help on that.