Has anyone else experienced a bug that a unit (in my case a Indian Armoured) is invisible and doesn't seem to exist? But it does show up when I want to go to the next turn as a unit I haven't given an order to

Yup has happened to me as well - twice with different armies, for no apparent reason. 

Ah, the infamous ghost unit strikes again! I've had that happen too, but with a British squad. geometry dash