Urgent: Balsa crashes on send / how to debug

Hi
I haven't changed Balsa nor its configuration. But my Gentoo system changes
nearly each day.
Suddenly, I cannot send emails with Balsa. It crashes all the time with:
Starting program: /usr/bin/balsa 
[Thread debugging using libthread_db enabled]
Using host libthread_db library "/lib64/libthread_db.so.1".
[New Thread 0x7fffe2d46700 (LWP 30677)]
[New Thread 0x7fffe1df8700 (LWP 30678)]
[New Thread 0x7fffe15f7700 (LWP 30680)]
** Message: init gpgme version 1.8.0
** Message: protocol OpenPGP: engine /usr/bin/gpg2 (home (null), version 2.2.0)
** Message: protocol CMS: engine /usr/bin/gpgsm (home (null), version 2.2.0)
** Message: protocol GPGCONF: engine /usr/bin/gpgconf (home (null), version 2.2.0)
** Message: protocol Assuan: engine /run/user/230/gnupg/S.gpg-agent (home !GPG_AGENT, version 1.0.0)
** Message: protocol UIServer: engine /run/user/230/gnupg/S.uiserver (home (null), version 1.0.0)
** Message: protocol Spawn: engine /nonexistent (home (null), version 1.0.0)
** Message: OpenPGP protocol supported
** Message: CMS (aka S/MIME) protocol supported
Network is available   (Thu 07 Sep 2017 07:47:48 PM CEST)
[New Thread 0x7fffe08b5700 (LWP 30693)]
[New Thread 0x7fffd30a8700 (LWP 30873)]

Thread 1 "balsa" received signal SIGSEGV, Segmentation fault.
0x00007ffff24748a7 in g_main_context_prepare ()
   from /usr/lib64/libglib-2.0.so.0
(gdb) where
#0  0x00007ffff24748a7 in g_main_context_prepare ()
   from /usr/lib64/libglib-2.0.so.0

I'd like to debug Balsa. But how to do this?
There lots of CFLAGS in different Makefiles.
Furthermore Install seems to strip the binaries.
Is there a recipe to prepare Balsa for source debugging?
Many thanks for a hint,
Helmut
P.S. This occurs with Balsa-2.5.3 as well as with the GIT version of Balsa.
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