PI JDBC INSERT Failed but message is registered as successful

Question

Dear all,
We have a scenario where we send an IDOC with prices of several materials to PI and then using JDBC we send it to an SQL database. During the mapping, we create an INSERT statement for each segment of the IDOC .
The problem is, that sometimes one or more insert statements may fail (the customer can see no new lines in the database), but in the monitoring everything seems ok . The message has a "processed successfully"  status so there is no way for the customer to know that something went wrong so each time they check the prices one by one .
The strange part is that if they find a mistake, they just resend the same message and after one or two tries it works ! This indicates that the problem is not in the actual data but somewhere else (probably in the database ?) .
So, one problem is why the data is not written and the second issue is why the message is logged as successful although one query has failed ,
Thank you all for your help .

Answer 1

Thank you for both for your quick response .
Unfortunately this scenario is up and running for quite some time already and the customer does not want to change it . Also, I am not sure how I could make an Insert statement that would include many lines .
Right now, the mapping produces the following result (I only post the first two statements, the actual number is around 500)
<Statement><dbTableName action="INSERT">
<table>min_sapsrs_price</table>
<access><STAT>0</STAT><
ACT_DATE>20100701</ACT_DATE>
<MOD_DEL>MOD</MOD_DEL>
<INTCODE>000000000014009003</INTCODE>
</access>
</dbTableName>
</Statement>
<Statement>
<dbTableName action="INSERT">
<table>min_sapsrs_price</table>
<access><STAT>0</STAT>
<ACT_DATE>20100701</ACT_DATE>
<MOD_DEL>MOD</MOD_DEL>
<INTCODE>000000000014009004</INTCODE>
</access>
</dbTableName>
</Statement>
could you please tell me how should I propose them to do it ?