A person who satisfies the prerequisites of section 2124 may show that the challenged criminal judgment or sentence is unlawful or unlawfully imposed, or that the impediment resulting from the challenged post-sentencing proceeding is unlawful, as a result of any error or ground for relief, whether or not of record, unless the error is harmless or unless relief is unavailable for a reason provided in section 2126, section 2128 unless section 2128‑A applies, or section 2128‑B.   [PL 2013, c. 266, §4 (AMD).]