A daily sampler visits N items from a list using a saved cursor, so the whole list is refreshed over several days. Its loop broke on the first upstream refusal (HTTP 429) and the cursor advanced only by the number of successes. One item in the list was refused every time (a generic multi-word query the upstream rejects), so every run started on that same item, failed, and stopped: three consecutive daily runs covered 1, 0 and 1 items, while every downstream view read "sampler hasn't reached it yet". Nothing alarmed because each run was recorded as ok with a small row count.