Thanks for your attention on this matter.

I applied your suggestion, and find la_error contains -1, according to MSDN help, there should be an error, or just the
record number that failed to be updated. Later i used AERROR(a_error) to find what is actually happened, but there is
nothing. Is there any way to know what exactly the error is? Furthermore, I tried this to other table that don't has the
problem, la_error also contains -1, and there is no problem after End Transaction.

Something interesting to the table is if I insert twice, there will be 2 record successfully appended to the table and then
every things back to normal.