I am doing a pg vector search, and when I have too many documents, it returns no results. Ideas?

CREATE INDEX "documents_embedding_idx" ON "public"."documents" USING "hnsw" ("embedding" "public"."vector_cosine_ops");

CREATE INDEX "documents_userId_idx" ON "public"."documents" USING "btree" ("userId");

CREATE OR REPLACE FUNCTION "public"."match_documents"("query_embedding" "public"."vector", "match_threshold" double precision, "match_count" integer, "userid" "uuid") RETURNS TABLE("id" "text", "chunktext" "text", "sourceId" "text", "similarity" double precision, "document" "jsonb")
    LANGUAGE "sql" STABLE
    AS $$
SELECT 
  documents.id, 
  documents."chunkText", 
  documents."sourceId",
  1 - (documents.embedding <=> query_embedding) AS similarity, 
  documents.document 
FROM documents 
WHERE 
  1 - (documents.embedding <=> query_embedding) > match_threshold 
  AND documents."userId" = userId
ORDER BY similarity DESC 
LIMIT match_count;
$$;