BEFORE triggers are dropped after pt-online-schema-change run

Create a table with 4 triggers BEFORE and AFTER; INSERT and UPDATE.
There is no FK.

PXC 5.7.30
pt-online-schema-change h=127.0.0.1,D=d,t=t --user=root --password=secret --preserve-triggers --alter "CHANGE COLUMN a a varchar(25) DEFAULT NULL" --alter-foreign-keys-method=auto --max-lag=10s --execute

After pt-osc run just two triggers left (only AFTER).

I can force pt-osc to keep all 4 triggers at:
create_triggers:
Comment out:
. " AND ACTION_TIMING = ? "
and $trigger_info->

{time}

,

For
my $trigger_sql = "SELECT TRIGGER_SCHEMA, TRIGGER_NAME, DEFINER, ACTION_STATEMENT, SQL_MODE, "
. " CHARACTER_SET_CLIENT, COLLATION_CONNECTION, EVENT_MANIPULATION, ACTION_TIMING "
. " FROM INFORMATION_SCHEMA.TRIGGERS "
. " WHERE EVENT_MANIPULATION = ? "
. " AND ACTION_TIMING = ? "
. " AND TRIGGER_SCHEMA = ? "
. " AND EVENT_OBJECT_TABLE = ?";