Translation plugin lost after upgrade

Translation plugin lost after upgrade

Hi,
I updated the plugin in question (subscribe mail), through WPMU Dashboard.
The upgrade is complete, I realized that the plugin was back in the original language (English).

I checked and in fact had been removed files of Italian .mo and .po.

Is there a way to avoid this annoying problem?
I'll have the same problem with the updates of all the plugins?
Every time I have to copy the files and some mo?

Thank you