No titlebar and no scrollbars in a gtk3 app in Plasma desktop

I'm using a GTK3 app called _Tilix_. It's a terminal app. I have 2 computers with KDE Neon based on __Ubuntu 16.04 LTS__. In one of them, _Tilix_ works ok. In the other one, no title bars and no scrollbars are painted. It is like they were transparent. Investigating a little, I've seen it uses the gtk3 theme called _Breeze_. No theme customization. I've tried to compare both computers, and to reinstall _Tilix_. How can I solve this? I think there must be some theme misconfiguration.