@Lucas.Sichardt: I am not sure for plain Android but for LineageOS and the f-droid app it was no problem to uninstall DC 1.40.0, force DC stop in the settings and then reinstall 1.38.2. BUT MAKE SURE TO BACKUP YOUR KEYS FROM ORIGINAL DC EXPORT FIRST!
Otherwise you might not be able to reinstall keys (even working ones) into DC as described in How to recover all chats after DC reinstallation?