TXW_HC_SEAT Error

Hello!

Can anyone tell me anything about TXW_HC_SEAT and/or HC map application sessions? Our box office manager is getting this error sometimes in Season Manager when trying to add hold codes:

Transaction Description: Updating seat map

Transaction Error: Row changed between retrieve and update.

No changes made to database.

UPDATE TXW_HC_SEAT SET hc_no = 930 WHERE seat_no = 9395 AND perf_no = 34933 AND session_no = 254247

I've been able to replicate the issue while following along with what's happening in TXW_HC_SEAT:

1.  In Season Manager search for one performance
2. Go to the Hold Codes tab and look at the seat map - at this point TXW_HC_SEAT is populated with all the seats, once row for each seat with a perf_no value of -1, and a second row for each seat with a perf_no value of the actual performance number
3. Go back to the Hold Codes tab and Expire Hold Codes using the "expire all" option -  TXW_HC_SEAT still has two rows per seat
4. Go to View Map, add some holds, click out to save it, and then get the above error. At this point only the rows in TXW_HC_SEAT with the -1 perf_no remain.

I don't fully understand what's happening, though it seems like this error is expected behavior if you move through Season Manager hold codes in this order? If anyone can explain it to me I'd be so grateful!

Thanks so much for any and all wisdom!
Sheela