Installing gnome-shell-extensions is not required to replicate this bug.

1) Install the gnome-shell-extension-dashtodock package; the detailed installation shell reports that portions of this package were replaced by gnome-shell-extension-ubuntu-dock.
2) Start the Tweak tool and select the extensions tab; Tweak tool will freeze and eventually abort.
3) Logout and login.
4) Start the Tweak tool and select the extensions tab; DashToDock is now included in the list of extensions.
5) Disable Ubuntu Dock; dock is not removed from the screen.
6) Enable DashToDock; eventually gnome-shell session aborts and GDM login screen is displayed.
7) Login; gnome-shell session starts to come up, but then aborts and GDM login screen is displayed.

Traceback from syslog:
Feb  6 18:45:40 panther2 org.gnome.Shell.desktop[3863]: == Stack trace for conte
xt 0x56332099b170 ==
Feb  6 18:45:40 panther2 org.gnome.Shell.desktop[3863]: #0 0x563320dc3d38 i   /u
<email address hidden>/theming.js:200 (0x
7f88ba230340 @ 201)
Feb  6 18:45:40 panther2 org.gnome.Shell.desktop[3863]: #1 0x7ffddc31b5d0 I   re
source:///org/gnome/gjs/modules/_legacy.js:82 (0x7f88f40c2bc0 @ 71)
Feb  6 18:45:40 panther2 org.gnome.Shell.desktop[3863]: #2 0x563320dc3c80 i   /u
<email address hidden>/theming.js:79 (0x7
f88ba22fef0 @ 451)
Feb  6 18:45:40 panther2 org.gnome.Shell.desktop[3863]: #3 0x7ffddc31c1e0 I   re
source:///org/gnome/gjs/modules/_legacy.js:82 (0x7f88f40c2bc0 @ 71)
Feb  6 18:45:40 panther2 org.gnome.Shell.desktop[3863]: #4 0x7ffddc31c2a0 b   re
source:///org/gnome/gjs/modules/_legacy.js:18 (0x7f88f40c2808 @ 36)
Feb  6 18:45:40 panther2 org.gnome.Shell.desktop[3863]: #5 0x7ffddc31c360 b   re
source:///org/gnome/gjs/modules/_legacy.js:114 (0x7f88f40c2d58 @ 178)
Feb  6 18:45:40 panther2 org.gnome.Shell.desktop[3863]: #6 0x563320dc3b60 i   /u
<email address hidden>/docking.js:363 (0x
7f88ba21a450 @ 2158)
Feb  6 18:45:40 panther2 org.gnome.Shell.desktop[3863]: #7 0x7ffddc31cff0 I   re
source:///org/gnome/gjs/modules/_legacy.js:82 (0x7f88f40c2bc0 @ 71)
Feb  6 18:45:40 panther2 org.gnome.Shell.desktop[3863]: #8 0x7ffddc31d0c0 b   re
source:///org/gnome/gjs/modules/_legacy.js:18 (0x7f88f40c2808 @ 36)
Feb  6 18:45:40 panther2 org.gnome.Shell.desktop[3863]: #9 0x7ffddc31d180 b   re
source:///org/gnome/gjs/modules/_legacy.js:114 (0x7f88f40c2d58 @ 178)
Feb  6 18:45:40 panther2 org.gnome.Shell.desktop[3863]: #10 0x563320dc3a98 i   /
<email address hidden>/docking.js:1744 (
0x7f88ba220a28 @ 259)
Feb  6 18:45:40 panther2 org.gnome.Shell.desktop[3863]: #11 0x7ffddc31de10 I   r
esource:///org/gnome/gjs/modules/_legacy.js:82 (0x7f88f40c2bc0 @ 71)
Feb  6 18:45:40 panther2 org.gnome.Shell.desktop[3863]: #12 0x563320dc3a08 i   /
<email address hidden>/docking.js:1678 (
0x7f88ba220890 @ 115)
Feb  6 18:45:40 panther2 org.gnome.Shell.desktop[3863]: #13 0x7ffddc31ea10 I   r
esource:///org/gnome/gjs/modules/_legacy.js:82 (0x7f88f40c2bc0 @ 71)
Feb  6 18:45:40 panther2 org.gnome.Shell.desktop[3863]: #14 0x7ffddc31eac0 b   r
esource:///org/gnome/gjs/modules/_legacy.js:18 (0x7f88f40c2808 @ 36)
Feb  6 18:45:40 panther2 org.gnome.Shell.desktop[3863]: #15 0x7ffddc31eb70 b   r
esource:///org/gnome/gjs/modules/_legacy.js:114 (0x7f88f40c2d58 @ 178)
Feb  6 18:45:40 panther2 org.gnome.Shell.desktop[3863]: #16 0x563320dc3980 i   /
<email address hidden>/extension.js:16 (
0x7f88bb8e2c48 @ 20)
Feb  6 18:45:40 panther2 org.gnome.Shell.desktop[3863]: #17 0x563320dc38d0 i   r
esource:///org/gnome/shell/ui/extensionSystem.js:129 (0x7f88d86b4670 @ 408)
Feb  6 18:45:40 panther2 org.gnome.Shell.desktop[3863]: #18 0x563320dc3838 i   r
esource:///org/gnome/shell/ui/extensionSystem.js:171 (0x7f88d86b4780 @ 241)
Feb  6 18:45:40 panther2 org.gnome.Shell.desktop[3863]: #19 0x563320dc37b8 i   r
esource:///org/gnome/shell/ui/extensionSystem.js:318 (0x7f88d86b4e68 @ 13)
Feb  6 18:45:40 panther2 org.gnome.Shell.desktop[3863]: #20 0x7ffddc31ff10 b   r
esource:///org/gnome/gjs/modules/signals.js:126 (0x7f88f40e2b38 @ 386)
Feb  6 18:45:40 panther2 org.gnome.Shell.desktop[3863]: #21 0x563320dc36d8 i   r
esource:///org/gnome/shell/misc/extensionUtils.js:184 (0x7f88d86b5a28 @ 360)
Feb  6 18:45:40 panther2 org.gnome.Shell.desktop[3863]: #22 0x7ffddc320ba0 I   r
esource:///org/gnome/gjs/modules/_legacy.js:82 (0x7f88f40c2bc0 @ 71)
Feb  6 18:45:40 panther2 org.gnome.Shell.desktop[3863]: #23 0x563320dc3640 i   r
esource:///org/gnome/gjs/modules/lang.js:97 (0x7f88f40d8450 @ 101)
Feb  6 18:45:40 panther2 org.gnome.Shell.desktop[3863]: #24 0x7ffddc322050 b   r
esource:///org/gnome/shell/misc/fileUtils.js:27 (0x7f88d86b5e68 @ 323)
Feb  6 18:45:40 panther2 org.gnome.Shell.desktop[3863]: #25 0x563320dc3580 i   r
esource:///org/gnome/shell/misc/extensionUtils.js:189 (0x7f88d86b5ab0 @ 97)
Feb  6 18:45:40 panther2 org.gnome.Shell.desktop[3863]: #26 0x7ffddc322cd0 I   r
esource:///org/gnome/gjs/modules/_legacy.js:82 (0x7f88f40c2bc0 @ 71)
Feb  6 18:45:40 panther2 org.gnome.Shell.desktop[3863]: #27 0x563320dc34f0 i   r
esource:///org/gnome/shell/ui/extensionSystem.js:320 (0x7f88d86b4de0 @ 200)
Feb  6 18:45:40 panther2 org.gnome.Shell.desktop[3863]: #28 0x563320dc3470 i   r
esource:///org/gnome/shell/ui/extensionSystem.js:328 (0x7f88d86b4ef0 @ 36)
Feb  6 18:45:40 panther2 org.gnome.Shell.desktop[3863]: #29 0x563320dc33f0 i   r
esource:///org/gnome/shell/ui/extensionSystem.js:359 (0x7f88d86b51a8 @ 67)
Feb  6 18:45:40 panther2 org.gnome.Shell.desktop[3863]: #30 0x563320dc3368 i   r
esource:///org/gnome/shell/ui/extensionSystem.js:367 (0x7f88d86b5230 @ 41)
Feb  6 18:45:40 panther2 org.gnome.Shell.desktop[3863]: #31 0x563320dc32c8 i   r
esource:///org/gnome/shell/ui/main.js:217 (0x7f88f40f5de0 @ 1066)
Feb  6 18:45:40 panther2 org.gnome.Shell.desktop[3863]: #32 0x563320dc3240 i   r
esource:///org/gnome/shell/ui/main.js:126 (0x7f88f40f5cd0 @ 236)
Feb  6 18:45:40 panther2 org.gnome.Shell.desktop[3863]: #33 0x563320dc31c8 i   <
main>:1 (0x7f88f4086ab0 @ 48)
Feb  6 18:45:40 panther2 gsd-xsettings[3993]: Failed to get current display conf
iguration state: GDBus.Error:org.freedesktop.DBus.Error.NameHasNoOwner: Name "or
g.gnome.Mutter.DisplayConfig" does not exist
Feb  6 18:45:40 panther2 dbus-daemon[789]: [system] Successfully activated servi
ce 'org.freedesktop.hostname1'
Feb  6 18:45:40 panther2 systemd[1]: Started Hostname Service.
Feb  6 18:45:40 panther2 gsd-rfkill[3975]: g_object_notify: object class 'CcRfki
llGlib' has no property named 'kernel-noinput'
Feb  6 18:45:40 panther2 kernel: [  746.692616] rfkill: input handler disabled
Feb  6 18:45:40 panther2 gsd-media-keys[4019]: Failed to grab accelerators: GDBu
s.Error:org.freedesktop.DBus.Error.ServiceUnknown: The name :1.25 was not provid
ed by any .service files (2)
Feb  6 18:45:40 panther2 gnome-session-binary[3724]: Entering running state
Feb  6 18:45:40 panther2 gnome-session[3724]: gnome-session-binary[3724]: WARNIN
G: Application 'org.gnome.Shell.desktop' killed by signal 5
Feb  6 18:45:40 panther2 gnome-session-binary[3724]: WARNING: Application 'org.g
nome.Shell.desktop' killed by signal 5