When I try to load and save vendor bill record in SuiteScript, I got an unexpected error This is my code and the error result.

var recObj = record.load({
                type: record.Type.VENDOR_BILL,
                id: 26466592
             })
             recObj.save();

Is there a field on the record labeled source?

We're seeing this crop up as well on multiple client accounts. Currently have a ticket open with NS.

Thanks, @Rob Witting

Can you ignore mandatory fields as true while saving the record. Might provide you a temporary solution.

Thanks, but the issue is already fixed this morning

This is what happens when you have a mandatory field that's not populated. Apparently Source became mandatory, perhaps in error.

The another reason can be a form. When you load/save the record with suitescript, it is working in the background open/submit UI form. NetSuite execute the script AS current user, and you should check what is the preferred form for that user. Another way is forcing which forn is used while script is executed (parameter forn in the load)