Can't find why Apex 4.0 is returning the following error?
If you copy and paste the error message into a fixed-width text editor, you'll will hardly notice that there is an extra space between the first double quotes and the name of the item, that I highlighted in red color.
Unexpected error, unable to find item name at application or page level. Error ERR-1002 Unable to find item ID for item " P33_LOCATION_ID" in application "21673".
When I inspected the branch action, I realized that I had inserted a blank between the comma and the item name in comma separated list of items and this breaks the toy.
Clearly item names are not trimmed by the internal PL/SQL function that does the splitting, so watch out for the extra blanks, they can drive you mad for a while.
I could not check yet if this happens in Apex 4.1.