Opening a user profile and his last actions on a small tablet it looks like this. The images are too big.
Yep, it appears at sizes from ~1000 down to ~500/400 pixels.
Below that limit the attachments are completely hidden, except for the header of the section.
It may be worth changing the css to use a display: inline-block on the table to let the images adapt better to the container.
If you want to try it out, this should work:
https://github.com/emanuele45/Dialogo/commit/32064f0ecc438e8ef8c3af9f64b244f329ec9c33