[WORKAROUND] mumble-1.2.6 (and 1.2.17) freezes on start

[netjiro]

I installed a fresh gentoo recently, up to date, tried to keep it small and simple.

mumble installs without any issues but doesn't start properly.
It brings up a blank window and freezes. Have to kill by ctrl-c in console or xkill.
tried starting as regular user and as root: same issue
tried building 1.2.17: but same issue as 1.2.6
tried building with only USE="alsa" and everything else off: same issue.

Running plasma, alsa, on a skull canyon nuc.
mumble is the first program that shows any weirdness thus far...

Can't figure out what could be wrong. Any good ideas as to what I should investigate next?

161208: also raised upstream: https://github.com/mumble-voip/mumble/issues/2702
and a gentoo bug: https://bugs.gentoo.org/show_bug.cgi?id=601980
including full gdb stack trace for all threads

[netjiro]

Upstream github issue thread comment:
https://github.com/mumble-voip/mumble/issues/2702#issuecomment-265876504

short:
* bug in mumble problem handling
* source of root issue probably in my system sound setup

[netjiro]

workaround found:
https://github.com/mumble-voip/mumble/issues/2702#issuecomment-267196223