first time posting here. Yay!
I've been having trouble with this dconf bug for some time now. And no solution on google seems to help.
To get this error all I need to do is try to change a setting. e.g.
Open preferences, change e.g. word size from 64 bits to 32 bits
close the preferences dialog
close the gnome-calculator application and a bunch of:
(gnome-calculator:18860): dconf-WARNING **: failed to commit changes to dconf: GDBus.Error:org.freedesktop.DBus.Error.UnknownMethod: No such method 'Change'
warnings pop up. Same thing happens if I want to change desktop background.