Somtimes duplicate manager deletes all versions
Sometimes (I have been unable to find out under what circumstances) clicking [x] in the duplicate manager deletes all versions of the file. Here's a screenshot; if I clicked 'Yes', it'd actually remove the raw file and all three sidecars.
While the behaviour of the [x] is not documented in the manual, I don't think that's how it's supposed to work.
darktable 2.6.1 from PPA
Ubuntu 18.04.2 LTS (Bionic Beaver)
Running Cinnamon as the desktop