diff --git a/lib/substantive_fixer.py b/lib/substantive_fixer.py
index 4d6dcd5..9bc7dbc 100644
--- a/lib/substantive_fixer.py
+++ b/lib/substantive_fixer.py
@@ -544,6 +544,14 @@ async def substantive_fix_cycle(conn, max_workers=None) -> tuple[int, int]:
         try:
             issues = json.loads(row["eval_issues"] or "[]")
         except (json.JSONDecodeError, TypeError):
+            # Corrupt JSON in eval_issues is abnormal (post-merge column drift,
+            # hand-edited row, partial write during crash). WARN so ops can chase
+            # the upstream column-write path. Without this, the row drops out of
+            # both substantive_rows and skipped_no_tags — the third silent path.
+            logger.warning(
+                "PR #%d: corrupt eval_issues JSON — skipping in substantive fix cycle",
+                row["number"],
+            )
             continue
         if set(issues) & (FIXABLE_TAGS | CONVERTIBLE_TAGS | UNFIXABLE_TAGS):
             substantive_rows.append(row)