I apologize if this has been mentioned before by someone else.
In the 'remove all' mode, buildings 'disappear' if you place them in an invalid location. e.g. in the ocean or forest. This only happens however if you only have one of the particular building. E.g. town hall, clan castle.
To try it, drag the town hall into the ocean, then tap somewhere else.
I tried it with my gold storages, I have two lvl 11s and one lvl 10. If I do it with my lvl 11 storages, all is fine. But, with my lvl 10 , it will also 'disappear'.
Other than that, all seems to be fine so far.
