LP:697557 - Wrong result with join_cache_level=3, BNLH join in maria-5.3-mwl128

After the most recent push to maria-5.3-mwl128, the following query:

SELECT t1.f2 FROM t2 JOIN t1 ON t2.f1 = t1.f1;

returns rows that do not match the ON condition.

Explain:

id select_type table type possible_keys key key_len ref rows Extra
1 SIMPLE t2 index f1 f1 13 NULL 1 Using where; Using index
1 SIMPLE t1 hash f1 f1 13 test.t2.f1 4 Using join buffer (flat, BNLH join)

test case:

SET SESSION SQL_MODE='NO_ENGINE_SUBSTITUTION';

CREATE TABLE t1 ( f1 varchar(10) , f2 int(11) , KEY (f1)) ENGINE=PBXT;
INSERT INTO t1 VALUES ('hgtofubnib',1),('GDOXZ',1492123648),('n',2),('fggxgalhgt',-2024407040);
CREATE TABLE t2 ( f1 varchar(10) , f2 int(11) , KEY (f1)) ENGINE=PBXT;
INSERT INTO t2 VALUES ('r',1);

SET SESSION join_cache_level=3;

SELECT t1.f2 FROM t2 JOIN t1 ON t2.f1 = t1.f1;

This particular test case is for PBXT, but the issue has been observed with other storage engines as well.