Hi Patrick,
Couple of thoughts:
1) Do you also have history table associated with BSEG. Did you check if that is consistent. Earlier I had a similar issue where SAP looked into HANA and mentioned that the history index was corrupt and asked me to restore the history table from the backup or something. Since we did not have the backup (it was on a test system), we closed the OSS message.
2) If you have some time time and memory to play around, can you please try
CREATE TABLE xxx like yyy with data;
-- this is very likely to fail with memory issue if your first large insert didn't go through.
Alternatively you can try
CREATE TABLE xxx like yyy with NO data;
and then try the insert into statements.
I am not completely sure if this will help simulate the corrupt issue.
Since SAP is also looking into index corruption, I am sure they will come up with something liking it back to earlier indexserver crash and you may have to ignore this as one stray incident. 
Regards,
Ravi