And it's another execution context, so there might be some scripts and workflows in play that become off/on because of the difference of execution context.

Yes that seems to be the best explanation for this behaviour. But I'm not sure how to troubleshoot this kind of a scenario. The thing is we don't have any scripts/workflows interacting with the Customer Deposit record, so it is strange that it fails for this particular record. I also have appropriate permissions in place and attached to the .ss file that triggers this code.

what about the customform parameter?

i tried messing around the customform value but it did not help. 😞