Percona with TokuDB crashes

We are using Percona 5.6.25-73.1 on Centos 7.1.1503 64bit with TokuDB plugin.

We have a pretty large database with around 2 TB data and about 1.5 Mio tables. The environment is mixed: MyISAM and (converted from MyISAM) TokuDB.

Since a couple of days we see frequent crashes of the server, mostly related to the following error in mysqld.log:

/mnt/workspace/percona-server-5.6-redhat-binary/label_exp/centos7-64/rpmbuild/BUILD/percona-server-5.6.25-73.1/storage/tokudb/ tokudb_compare_two_keys: Assertion `Handlerton: (uint32_t)(new_key_ptr - (uchar *)new_key_data) <= new_key_size ’ failed (errno=2)
: No such file or directory

Two crashes were “got signal 11”, one crash “got signal 6”.

Any idea regarding this?