Bug 1933633 is a clean exit whereas this bug 1960336 is a segfault. So the two bugs should be kept separate.
We can make this bug about both your issues though: (a) fprintd crashes with SIGSEGV; and (b) login screen can't survive fprintd failure.
Next please follow the steps in https://wiki.ubuntu.com/Bugs/Responses#Missing_a_crash_report_or_having_a_.crash_attachment to look for the fprintd crash.
Bug 1933633 is a clean exit whereas this bug 1960336 is a segfault. So the two bugs should be kept separate.
We can make this bug about both your issues though:
(a) fprintd crashes with SIGSEGV; and
(b) login screen can't survive fprintd failure.
Next please follow the steps in https:/ /wiki.ubuntu. com/Bugs/ Responses# Missing_ a_crash_ report_ or_having_ a_.crash_ attachment to look for the fprintd crash.