There's a failed assertion when entering battle. Same behavior with skirmishes:
Assertion failed: (selChr), function CL_ActorSelect, file src/client/cl_actor.c, line 818.
0 ufo 0x00147f8c Sys_Mkdir + 126
1 ufo 0x00147fd9 Sys_Mkdir + 203
2 libSystem.B.dylib 0x91ac42bb _sigtramp + 43
3
0xffffffff 0x0 + 4294967295
4 libSystem.B.dylib 0x91b3823a raise + 26
5 libSystem.B.dylib 0x91b44679 abort + 73
6 libSystem.B.dylib 0x91b393db __assert_rtn + 101
7 ufo 0x00003a64 CL_ActorSelect + 420
8 ufo 0x00003b24 CL_ActorSelectList + 85
9 ufo 0x00003766 CL_AddActorToTeamList + 361
10 ufo 0x000311bf CL_DrawLineOfSight + 2177
11 ufo 0x0003226f CL_DrawLineOfSight + 6449
12 ufo 0x000ed49c Qcommon_Frame + 180
13 ufo 0x0014843b main + 307
14 ufo 0x00001d1e start + 54
15
0x00000004 0x0 + 4
LE_Cleanup: Clearing up to 3 unused LE inventories
Shutdown gametype 'Skirmish mode'
Shutdown server: Quitting server.
==== ShutdownGame ====