SCC_Init fails to initialize ReadHandle_Lan/WriteHandle_Lan for the second channel to -1 but SCC_UnInit will later try to close(0) for these. This causes a crash when my libretro core version is closed for the second time, and 0 has already been closed. Closing 0 was already a problem, but it's just not a crash the first time, so it wasn't noticeable in the standalone version.
The fix is simple, just initialize them:
SCC.Chn[1].ReadHandle_Lan = SCC.Chn[1].WriteHandle_Lan = -1;
https://git.tuxfamily.org/hatari/hatari.git/tree/src/scc.c#n506-- Brad Smith