SDL2 applications crashing with SIGBUS

Hello

I'm using the sparc64 port of NetBSD 8.0 on my Sun Ultra 10 with a
Creator3D card. The system itself is running fine.
But when I wanted to try out some SDL2-based games compiled from
source, I'm only getting SIGBUS crashes (probably due to some
unaligned memory access).

Running the games through gdb I get:

Chocolate doom (both chocolate-doom and chocolate-doom-setup):
Thread 1 received signal SIGBUS, Bus error.
0x0000000043c9a534 in XkbSetDetectableAutoRepeat () from
/usr/pkg/lib/libX11.so.6
(gdb)

Dune Legacy gives the same error:
Program received signal SIGBUS, Bus error.
0x000000004209a534 in XkbSetDetectableAutoRepeat () from
/usr/pkg/lib/libX11.so.6
(gdb)

tyr-quake gives a similar segfault:
Program received signal SIGSEGV, Segmentation fault.
0x0000000040923ca4 in XChangeKeyboardControl () from /usr/pkg/lib/libX11.so.6
(gdb)

So, is there a sparc-specific problem in libX11.so.6 in the keyboard section?
Or is the way the SDL2 applications are calling the library wrong?

Has someone experienced similar issues, or has ideas how to continue
with troubleshooting?

Best regards
Elias