Some updates on this bug:

I've tested several VcXsrv-Versions from http://code.x2go.org/releases/binary-win32/3rd-party/vcxsrv-modified-by-x2go... The bug purely occurs with the more recent versions of VcXsrv - like 1.15.2.0 and 1.15.2.1 The bug does NOT occur with the older versions 1.14 (tested 1.14.3.2).

So the bug is caused by changes made in VcXsrv from version 1.14 to 1.15. I used the debug version "vcxsrv-debug.1.15.2.1-xp+vc2013+x2go1.installer.exe" to receive the following trace of the SIGFAULT:

Program received signal SIGSEGV, Segmentation fault. in memcpy () from C:\Temp\VcXsrv-Debug\msvcr120d.dll

0x5b4b3365 <+0x01c5> f3 0f 6f 0e movdqu (%esi),%xmm1 0x5b4b3369 <+0x01c9> 83 e9 10 sub $0x10,%ecx 0x5b4b336c <+0x01cc> 8d 76 10 lea 0x10(%esi),%esi 0x5b4b336f <+0x01cf> 66 0f 7f 0f movdqa %xmm1,(%edi) 0x5b4b3373 <+0x01d3> 8d 7f 10 lea 0x10(%edi),%edi 0x5b4b3376 <+0x01d6> eb e8 jmp 0x5b4b3360 <memcpy+448> 0x5b4b3378 <+0x01d8> 0f ba e1 02 bt $0x2,%ecx 0x5b4b337c <+0x01dc> 73 0d jae 0x5b4b338b <memcpy+491> 0x5b4b337e <+0x01de> 8b 06 mov (%esi),%eax 0x5b4b3380 <+0x01e0> 83 e9 04 sub $0x4,%ecx 0x5b4b3383 <+0x01e3> 8d 76 04 lea 0x4(%esi),%esi 0x5b4b3386 <+0x01e6> 89 07 mov %eax,(%edi) 0x5b4b3388 <+0x01e8> 8d 7f 04 lea 0x4(%edi),%edi 0x5b4b338b <+0x01eb> 0f ba e1 03 bt $0x3,%ecx 0x5b4b338f <+0x01ef> 73 11 jae 0x5b4b33a2 <memcpy+514> 0x5b4b3391 <+0x01f1> f3 0f 7e 0e movq (%esi),%xmm1 0x5b4b3395 <+0x01f5> 83 e9 08 sub $0x8,%ecx 0x5b4b3398 <+0x01f8> 8d 76 08 lea 0x8(%esi),%esi 0x5b4b339b <+0x01fb> 66 0f d6 0f movq %xmm1,(%edi) 0x5b4b339f <+0x01ff> 8d 7f 08 lea 0x8(%edi),%edi 0x5b4b33a2 <+0x0202> 8b 04 8d d8 34 4b 5b mov 0x5b4b34d8(,%ecx,4),%eax 0x5b4b33a9 <+0x0209> ff e0 jmp *%eax 0x5b4b33ab <+0x020b> f7 c7 03 00 00 00 test $0x3,%edi 0x5b4b33b1 <+0x0211> 75 15 jne 0x5b4b33c8 <memcpy+552> 0x5b4b33b3 <+0x0213> c1 e9 02 shr $0x2,%ecx 0x5b4b33b6 <+0x0216> 83 e2 03 and $0x3,%edx 0x5b4b33b9 <+0x0219> 83 f9 08 cmp $0x8,%ecx 0x5b4b33bc <+0x021c> 72 2a jb 0x5b4b33e8 <memcpy+584> SEGFAULT 0x5b4b33be <+0x021e> f3 a5 rep movsl %ds:(%esi),%es:(%edi)