Finally I have the solution (I think so) but not the reason.

In a set of experiments, I was really puzzled.

Factions with saved game issues: dacia (padane gauls), romans_scipii (italic peoples) and carthage (idem).

Factions without saved game issues: gauls (idem), romans_julii (romans) and greek_cities (greek colonies).

In the campaign I had the senate as superfaction of only romans_julii, but I got messages of proscription of both julii and scipii, and also the messages were messed up, as the message appeared for julii when the scipii were proscripted.

Moreover, although the senate was not superfaction of romans_scipii, when playing with them I received missions and rewards. That means (I think so) that in the case of one faction is included in the superfaction system, all the roman factions present in the campaign are automathically included in the system.

In view of that, I eliminated all traces of superfaction system, and now romans and gauls don't produce saved game issues. I didn't have time to test all the other factions, but it seems this question was the origin of the problem.