I recently ran into this problem with the Google ads on COM-101 (Rocky Mountains), and it's very irritating to say the least.
Travian and other videos work fine, but the last few days most viedos has been Google ads and thus just ends up in a blank screen and no reward at all. I've cleared cache/cookies (standard procedure for almost any error), and also raised a ticket (which has been forwarded to development).
This seems to be a well known bug since long, so why is it still around?
Com101 Rocky Mountains
Derailed Tom, COM101 Rocky Mountains
COM101 Golden Gate
Another quite annoying (to say the least) thing with the Android app is that it periodically freezes (the UI doesn't respond at all), this is also (as above) not clearly replicable but happens every now and then. Sometimes when returning from a subscreen (research for example) the whole UI get completely unresponsive, and the only way to get back in action is to terminate the app and restart it.
Yet another thing that forces one to terminate and restart is loss of server connection, which can happen when setting a schedule for example when the grayed train logo will get stuck infinitely. You can also see that when entering messages, industries, cities etc where you get no avatars or data, and the only way to get'em back is to force restart.