So far I haven't been stopped by J2 yet, but I'm sure it's bound to happen sooner or later.
I know that the penalties for having an unlicensed weapon is very serious here. How would these guys see it that I have an expired permit but also have the receipt from Ban Reservas showing I've paid the renewal fee and the receipt from the lab where I did the anti doping test? I just haven't got round to taking it to SD to do the ballistics test yet.
Depends on the current situation with licenses. For example, last year in September it was the same situation with lack of plastic (or broken printer, etc), but it was an official Aviso on MIP's website that people who paid for renewals can carry the gun with the expired license and all receipts. So I had this document printed with me for a month, just in case, but I also called them and they said that all street patrols know about that. Finally, I got my new license with one month delay.
Right now there is nothing on their website about any delays or lack of plastic, so you can call them and ask. But if it's your fault and you are just too lazy to go to ballistic test, you may have troubles if they stop you.