Hi polonus, thanks for your pointers.
I've already checked most of the sites, and besides some recommendations and best practices that could be followed, none of that justifies Avast to classify the santander.com.uy domain as phishing.
The main questions here are:
Why Avast is classifying as phishing a site which obviously isn't.
Why does it take so long on their part to respond, given that there are customers complaining online about it for hours.(see attached image)
This is is really damaging on many ends, not justifiable on an outdated jquery library.