[Official Census docs (NetSuite sync troubleshooting)]: NetSuite sync errors almost always come from sublist fields. Sublist fields must be sent as arrays of objects, names are case-sensitive and must match the API schema exactly, and custom fields need the ScriptID (for example custcol_example_field), never the label. Use the NetSuite Schema Browser to confirm a field exists on the exact sublist (itemList, lineList, applyList), and for custom fields confirm it was created as a Transaction Line Field, not a body field. `Passed nil into T.must` means a configured field could not be found or resolved, usually a sublist field on the wrong record type or a recently added field not yet in the API.

Context: Official docs (Census/Activations NetSuite sync troubleshooting): documents the most common source of NetSuite sync errors: sublist (line-level) fields. Field names are case-sensitive, must match the API schema exactly, and custom fields must be referenced by ScriptID, not the display label. The error `Passed nil into T.must` usually means a field could not be resolved.