Damaged binlog index

Few times we got damaged binlog index on two of our servers running MariaDB 10.0.20.

I can't tell anything exact, but.

Once index looked fine, but probably included invisible symbols, and none of master command were working (RESET MASTER, SHOW MASTER STATUS).

Another time index got some binary data (attached). This happened on master and slave (both running the same version - 10.0.20, and have the same config)

Yet another time index on master has something on the first line and mysqldump --master-data=1/2 caught SIGSEGV permanently:

# mysqldump --master-data=2 --single-transaction=1 --compact=1 --comments=0 bob_live_tw > /dev/null

Segmentation fault (core dumped)

mysqld printed something weird on stderr (attached).