I posted a separate thread last month. I paid the overstay fee at EZE and didn't know if I'd have problems coming back in. I came back 2 weeks ago to EZE from Miami and had no issues at all even though I overstayed. Several friends have paid the overstay fee or doing border runs and not had problems.
My neighbor is a Russian and her cousin tried entering Argentina at 7 months pregnant and was rejected at EZE. Apparently, they are aware of many Russians try to have kids here. They are letting some in but turning away others.