This short note identifies the local support structure of two visible image-side walls in endpoint-compression word fibers. For the determinant-zero wall uv=wuv=wuv=w, the paper proves that no nonzero-coefficient AAA-chart fiber points exist; any such solution forces coefficient collapse. For the endpoint wall u=1u=1u=1, the paper shows a distinct support-level decomposition into a terminal-letter branch and an inherited truncated-chart boundary. The results clarify the relation between determinant collapse, parity boundaries, and endpoint-wall structure in the GMA series.