Can a seller refuse to update a schedule even after finding out it's inaccurate?

Not without real risk. If a seller knows a schedule is inaccurate and refuses to correct it before closing, that generally isn't a neutral choice — since the schedule supports a specific representation, knowingly leaving it wrong means the seller is, in substance, standing behind a representation it knows to be false, which is a much more serious problem than an innocent, unnoticed error.

Depending on how the agreement is worded, a buyer who learns a seller is refusing to fix a known inaccuracy may have several responses available: refusing to close on the basis that a bring-down condition (that the representations remain true) isn't satisfied, pursuing a separate breach or misrepresentation claim once the true facts are known, or negotiating a specific price adjustment or side indemnity to close anyway with the issue accounted for. A knowing refusal to correct also tends to undercut a seller's ability to later argue any related knowledge qualifier protects it, since the seller plainly did know.

If you're a buyer facing this situation, document exactly what you were told and when, and get a Treadstone business lawyer involved before deciding whether to proceed to closing on those terms.