I enabled the firewall, and it seems that everything is ok... I no longer see untranslated packets on the outside interface...

so, the workaround should be adding
name dropinvalid {

default-action accept
rule 10 {
    action drop
    state {
        invalid enable
    }
}

}

Actually, that router is supposed not to do any filtering.
anyway, it is unclear to me where do you want me to configure the firewall rules: usually the "allow established and related" rule is configured in input on the outside interface of the firewall (in my case, eth0), while I have problems with packets EXITING eth0, and coming from eth1.
I should allow ANY packet coming from eth1 to exit from eth0, with their address translated (otherwise, how can a client pc, connected to eht1, start a NEW connection to the outside world?

I uploaded the two captures.

I installed 1.2.0beta1 ... it shows the same problem.

We use vmxnet3 adapters