The following script exhibits a bug in SQLite versions 3.41.0, 3.41.1, 3.41.2, and trunk:

CREATE TABLE user
( id  INTEGER NOT NULL PRIMARY KEY
, tag INTEGER );
CREATE INDEX "user(-tag)" ON user(-tag);

CREATE TABLE marker
( type    INTEGER NOT NULL
, user_id INTEGER NOT NULL
, value   INTEGER NOT NULL );

INSERT INTO user   VALUES (0, 7), (1, 8);
INSERT INTO marker VALUES (0, 0, 100), (0, 1, 101);

SELECT u.tag, v.max_value
FROM (SELECT tag FROM user GROUP BY -tag) u
JOIN (SELECT u.tag, m.type, MAX(m.value) AS max_value
      FROM user u
      JOIN marker m ON m.user_id = u.id
      GROUP BY m.type, u.tag
     ) v ON v.type = 0 AND v.tag = u.tag;

The buggy versions of SQLite produce the incorrect output 7|7,8|8, while earlier versions produce the correct output 7|100,8|101. The incorrect output depends on the presence of the index on user(-tag); if the index is removed, the buggy versions also produce the correct result. This bug seems rather bad to me.