systemctl isolate multi-user.target not working?

In Ubuntu 16.04 I tried to switch from the default graphical.target to multi-user.target with systemctl isolate multi-user.target,
and all I get is a black screen with some disk info in the upper-left coer. The target unit is there (state is static), as shown by systemctl list-unit-files.
What's up?
I tried the same command on suselinux Leap 42.1, it worked perfectly. Also, on suselinux Leap 42.1, I used systemctl isolate graphical.target to retu to the full GUI runlevel, no problem.

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