I discovered an error while trying to save my attachments. The system was not saving the title attribute. I analyzed the code, and found a typo.

Where was: title_attibute
I changed to: title_attribute

administrator\components\com_k2\models\item.php

K2 2.10

Thanks!

There is another problem that I fixed on my own. If the user clicks add an attachment, and saves without selecting any files, an unexpected error occurs in the frontend. I created a function with JS so that the article cannot be saved if an attachment is empty. I think it would be interesting to implement this natively in K2.