I'm getting

ERROR: Field 'line' Not Found

for a field called # which represents the line number. (purchase orders, before load, on create) I've undeployed every script and workflow on the record (as evidenced on the scripted records chrome extension). I've cleared my cache. There is no custom code on the form.

Uhmm beforeLoad on create you have no lines at all right?

Yes

So, what are you trying to do with the line field?

I'm working on something unrelated. Just want to fix the bug.

What I'm trying to say is there is no lines on beforeLoad on create, are you saying you do have lines?

that's probably it

My guess is the field is sourcing its value from the line field, and there is no line field in the form (at least not accessible yet). You can play with NVL2 but not sure if that would solve your problem.