The main issue is that the ads appear at the top of the screen and their position prevents access to certain tabs.
That shouldn't happen. I sent you mail about it.
If it helps I can reproduce this consistently by task switching. If I switch away from the app, when I return there is an ad at the top of the screen, overlaying the UI as it has not reserved space for it.
If I go into settings and enable ads, the UI shifts to accommodate it and the ad is replaced (or perhaps overlaid) with a completely new ad. If I disable ads again, the UI shifts back to fill the screen and I see the first ad again.
Dismissing the app and reloading solves the issue, but task switching reintroduces it again without fail. I'm running android 7.0.