Since this is a post-processing BPM, if you update the physical table (quoteDtl) you will get a Row has been modified message when you come back to the quote screen. If you update the temporary table in a post processing BPM you need to save the screen before exiting or the change will rollback. There are some other approaches when updating in a post-processing that have been discussed in other messages on the group.
I haven't looked at the method you are triggering the BPM but you may want to consider moving this to a pre-processing BPM and only work with the temporary tables. Changes in the pre-processing stage will not generate a row modified message and the main method will make the changes permanent or at least properly stage them for later saving.
Encompass Solutions, Inc