@meleast:
Thanks for contacting us and reporting this issue! It sounds like you ran into a really bad bug, but we haven’t had any other reports of this yet.
Does this appear to happen everywhere in Switzerland when you zoom in?
Do you have Wikipedia installed? If so, perhaps try going to Settings > Manage Data and disable Wikipedia to see if it is still happening..
Could you tell us what the app says the download size is for Switzerland? This will help tell us if certain files somehow got corrupt on download.
Also, can you try switch Pocket Earth into Offline mode in the settings side menu and see if the issue still occurs?
Lastly, you could try deleting and reinstalling the app, although you will loose any saved Favorites and map data.