The following SQL generates an extra, incorrect result row:

CREATE TABLE t1(x TEXT);
CREATE TABLE t2(y TEXT);
INSERT INTO t1 VALUES('good'),('bad');
INSERT INTO t2 VALUES('good'),('bad');
SELECT * FROM t1 JOIN t2 ON x=y
 WHERE x='good' AND y='good';

This problem was reported on the mailing list by Jim Bosch. Bisecting shows that the malfunction was introduced by check-in [1c3e5c20a9e6f501] on 2020-01-08. That check-in appears in versions 3.31.0 and 3.31.1.