IMPORT TABLESPACE is hanging in the 'System lock' state

We have a development database server with Percona-server 5.7.15-9 on it. It replicates two schemas from two different production servers using multi-source GTID replication. Lets call these schemas alice and bob. On the dev server we clone this replicas of production databases to get databases for development. They are called 1_alice, 1_bob, 2_alice, 2_bob, etc. All of them use the same instance of MySQL. For fast cloning we use Percona XtraBackup as described here https://www.percona.com/doc/percona-xtrabackup/2.4/innobackupex/restoring_individual_tables_ibk.html In the past there were only one replica (alice) and we used binary log position for replication instead of GTID. These times everything worked fine and fast. One day (I'm not sure when exactly) it became broken. Now when I perform ALTER TABLE 2_alice.access_group IMPORT TABLESPACE query, it hangs in the 'System lock' state. And could be hanging in this state from 1 min 'till 1 hour and more (then it works). There are no more active connections instead of two replicas, but they doesn't use 2_alice schema. Why is IMPORT TABLESPACE query hanging and how could I debug this case?